As the 21st century gathers pace, it’s clear we’re living through a golden age of scientific discovery. From rewiring our understanding of the Universe to reshaping the tools of everyday life, breakthroughs once thought impossible are now shaping the world around us.
To reflect on the progress so far, we asked some of the world's leading thinkers to spotlight the groundbreaking scientific breakthroughs that have transformed our world since the turn of the millennium.
1. Dream engineering
Until the turn of the last century, psychologists often argued that dreaming was a meaningless experience best confined to the fringes of science. But the 21st century has witnessed a surge of scientific interest in our nocturnal adventures and produced a steady stream of articles exploring the psychology of dreaming.
Some of this work has explored how dreaming can help people process negative emotions and prepare them for challenging events in the real world. Another strand of research has explored the link between dreams and creativity, and has shown that our dreaming minds often come up with new and innovative solutions to pressing problems.
There’s also work that has looked at the social side of dreaming, with psychologists arguing that discussing a dream with others is an effective way of forming and maintaining caring relationships.
Other scientists have taken a different approach and developed techniques that allow them to communicate with people experiencing a lucid dream.
Finally, there’s dream engineering, wherein researchers use smells, sounds and suggestions to manipulate our dreaming minds.
For years, trying to convince scientists to take dreams seriously was a nightmare. Now the tide has turned and we’re starting to uncover the many ways in which dreaming makes a vital contribution to our waking lives.
By Prof Richard Wiseman, Professor of the Public Understanding of Psychology, University of Hertfordshire; Author of Magic Your Mind Happy
2. A new type of stem cell
Before 2006, if researchers wanted to work with human embryonic stem cells, they had to work with human embryos. This was ethically charged territory – the embryos were leftovers from fertility treatments and were destroyed in the process.
Then Prof Shinya Yamanaka from Kyoto University devised a way to make embryonic stem cells without using embryos.
By adding a handful of genes into cultured skin cells and nurturing them with certain nutrients, adult cells could be reprogrammed to become ‘induced pluripotent stem (iPS) cells.’
‘Pluripotent’ means that these lab-made stem cells can turn – or ‘differentiate’ – into many other types of cells, including heart cells and neurons.
Now researchers can take cells from an adult animal, turn them into iPS cells and then turn them into the specialised cells of their choice. iPS cells are now routinely used to help test new drugs and therapies, but perhaps their most exciting use is in the field of regenerative medicine.
Imagine a patient with heart disease. Now imagine taking some of their skin cells and using iPS technology to create a pool of healthy heart cells.
The replacement tissue could then be transplanted into the patient’s heart to repair it, and because the cells are the patient’s own, there would be no danger of the tissue being rejected.
The same method could be applied to other conditions such as Alzheimer’s disease and kidney failure, raising the prospect of cures for currently incurable diseases.
Such brilliant, versatile cells… It’s no wonder that Yamanaka received a Nobel Prize in 2012 for his work in their discovery.
By Dr Helen Pilcher, author, speaker and science communication consultant
3. Global heating
Only by looking into the past can we get an inkling of the seriousness of today’s climate predicament.
The terrifying reality is that the global average temperature rise, which is now teetering on the edge of the 1.5°C dangerous climate breakdown guardrail, is occurring 50 times faster than when the world warmed after the Ice Age.
That was 56 million years ago, during the Palaeocene-Eocene Thermal Maximum (PETM).
The episode of rapid heating saw dead, oxygen-depleted oceans and sea levels 50m higher than they are now. And the global temperature today is ramping-up at least ten times faster than during the PETM.
We’re in the middle of a unique climate experiment, continually pumping out 40 billion tonnes of carbon dioxide every year, and hoping that it’ll be fine. I can tell you now, it won’t be.
By Prof Bill McGuire, Professor Emeritus of Geophysical & Climate Hazards, UCL; Author of Hothouse Earth: An Inhabitant's Guide
4. Attribution analysis
In a nutshell, attribution analysis seeks to determine the extent to which global heating has influenced a particular extreme weather event, such as increasing its intensity or raising its likelihood.
It involves running two computer simulations. One assumes today’s artificially heated climate, the other assumes a pre-industrial climate with all the human influences removed.
Comparison reveals whether global heating had an effect and, if so, what it was. The first-ever attribution analysis determined that the 2003 European heatwave (which claimed 70,000 lives and saw temperatures breach the 37°C/98°F mark for the first time in the UK) was made twice as likely by global heating.
Attribution analysis sheds light on the growing impact global heating is having on our weather patterns, while also loudly undermining the climate deniers – a win all round.
Prof Bill McGuire, Professor Emeritus of Geophysical & Climate Hazards, UCL; Author of Hothouse Earth: An Inhabitant's Guide
5. mRNA vaccines
The use of mRNA for various medical applications has been in development for decades. It wasn’t until the COVID-19 pandemic that the impact of the technology was first felt, however.
mRNA vaccines allow for the development of vaccines far more quickly than was previously possible – two months for COVID-19 compared to the previous record of four years.
It’s estimated that the COVID-19 mRNA vaccines saved nearly 20 million lives in their first year of use.
In the coming years, we’ll likely have a range of new mRNA vaccines for other viruses that change regularly, like the flu, as well as for viruses that haven’t responded well to previous vaccine technology, like HIV.
By Dr Jeremy Rossman, Honorary Senior Lecturer in Virology, University of Kent
6. The Human Genome Project
In 1990, scientists began to sequence the human genome. It took until 2022 to produce a complete sequence.
This achievement has profoundly changed biomedical science, allowing for research and technology that wouldn’t be possible otherwise, like using CRISPR to modify genetic diseases.
We’re just starting to feel the impact of this achievement on medical practice. By knowing our genome, it’s possible to find changes in genes that are associated with, or even cause, various diseases.
This increases our understanding of those diseases, as well as our ability to diagnose and treat them.
By Dr Jeremy Rossman, Honorary Senior Lecturer in Virology, University of Kent
Read more:
- Nuclear clocks: How ultra-precise measurements will let us probe the Universe like never before
- How close are we to mass-producing humanoid robots?
- 10 of the world's worst-ever inventions
7. Solving the 'einstein' problem
I believe the most important mathematical breakthrough this century is the solution to the long-standing ‘einstein’ (one-stone) problem.
The einstein problem asks whether there is a shape that can tile an infinitely large horizontal surface so that the pattern never repeats.
Brilliant minds had searched for decades for such shapes. Then in 2022, David Smith, a retired print technician and amateur maths enthusiast, began working with software and cardboard cut-outs at his home in Bridlington, Yorkshire.
Smith had worked for years on tiling patterns and had a strong intuition his shape, nicknamed the ‘hat’, would both tile the surface and never repeat.
He didn’t have the mathematical tools to prove his hunch, however, so he turned to the community of tiling enthusiasts and got help from Prof Craig Kaplan at the University of Waterloo, Canada; Prof Chaim Goodman-Strauss from the University of Arkansas; and software engineer Dr Joseph Myers from Cambridge.
Together they came up with computer-based and analytic proofs for a whole family of shapes, and their preprint study was greeted with international acclaim in March 2023 – even though the ‘hat’ occasionally needed to be flipped over to successfully tile the plane.
But no sooner had the preprint of their work been released, than David came up with the ‘spectre’ – a chiral aperiodic monotile, which didn’t need flipping.
Even more impressive, the ‘spectre’ was a member of a larger class of such tiles that allows the straight edges to be wavy.
Again, his colleagues proved the truth of his intuition. This was a beautiful achievement, led by an extraordinary mathematical hobbyist.
By Sir David Spiegelhalter, Emeritus Professor of Statistics, University of Cambridge
8. The cure for HIV
There was a time when HIV was a death sentence. Then anti-retroviral drugs came along and prospects improved. More and more people became able to live with the disease, but a cure still seemed like a distant dream.
Then in 2007, an HIV-positive man called Timothy Ray Brown received a bone marrow transplant for his leukaemia. Chemotherapy had failed and Brown was running out of options.
His doctor, Dr Gero Hütter, thought that the treatment might be able to cure his cancer, but he also realised that if he could find a donor who was genetically resistant to HIV, there was a chance that the same treatment might also cure his HIV.
Some people are naturally HIV-resistant. They carry a mutation in a gene called CCR5, which codes for a receptor protein that HIV uses to enter host cells.
After scouring the register, Hütter found a donor who not only matched Brown’s immune profile, but also carried two copies of the mutated gene.
The transplant went ahead and a few years later, researchers could find no trace of HIV in Brown’s body. Brown came off his anti-retroviral meds and went on to live the rest of his life HIV-free.
He was the first person to be cured of HIV.
Since then, at least six more people with cancer have been cured of HIV using bone marrow transplants.
The treatment, however, is brutal, with risks so great that it’s unlikely ever to become a routine procedure, but it has taught researchers a great deal about HIV and given hope to the world that a cure for HIV will, one day, be possible.
By Dr Helen Pilcher, author, speaker and science communication consultant
9. Transformers and large language models
Artificial Intelligence (AI) has been in the news for more than a decade, largely because one key AI technology – neural networks – finally started to work at scale.
The new AI era was heralded by the advent of ‘deep learning’ around 2005, driven by cheap computer power and plentiful data for ‘training’ neural nets.
The field exploded and we began to see a host of impressive applications. AI hit the headlines.
And then, something unexpected happened. In 2017, a Google team published a scientific paper describing a new architecture for organising neural nets – the so-called ‘transformer architecture.’
The transformer architecture is a neural network architecture for token prediction: taking as input a sequence of tokens (words) and then predicting the next token (word) to appear.
They’re trained by feeding them ordinary human text, and given a ‘prompt’ (for example: ‘a summary of Winston Churchill’s life’). They’ll then try to predict the word most likely to appear next. They do this one word at a time, but the process can be repeated over and over.
It wasn’t obvious in 2017 that transformers would be so… transformative. To realise their full power, you had to be prepared to build them on an unprecedented scale, throw mind-boggling quantities of training data at them and train them with AI supercomputers running for months.
Google didn’t make that bet; it was a little-known organisation called OpenAI, supported by Microsoft. And it paid off, spectacularly.
The first real hint that we were entering a new era was the release of GPT-3 in June 2020. Those with access to OpenAI’s new program seemed genuinely startled by how capable it was.
Just as remarkable for AI researchers was its emergent capabilities: the ability to do things that it wasn’t designed to do.
Questions, like the famous Turing Test, which had been of strictly philosophical interest previously, suddenly became practical experimental questions.
The unprecedented success of Large Language Models (LLMs) like ChatGPT took Silicon Valley by surprise and now the world’s richest companies are pivoting to try to embed this remarkable new technology everywhere, in the hope that they’ll find the killer application.
For all their success, LLMs aren’t the end of the road for AI; the dream of a helpful household robot that can clear your dinner table and load the dishwasher still seems frustratingly distant.
But the technology is astonishing nonetheless. We’re living at a remarkable time in technological history: our history will be divided into pre-GPT and post-GPT.
By Prof Michael Wolldridge, Ashall Professor of the Foundations of Artificial Intelligence, University of Oxford
10. HPV vaccine
At the turn of the century, scientists knew that cervical cancer was caused by Human Papillomavirus (HPV). Of over 200 known HPV strains, two high-risk types – 16 and 18 – are responsible for over 70 per cent of cervical cancer cases.
While the UK’s cervical screening programme, launched in the 1960s, successfully reduced cervical cancer rates, a huge shift came with the introduction of the HPV vaccine.
The vaccine became part of the UK’s national programme in 2008. Today, it’s licensed in over 100 countries and offered to both girls and boys to prevent HPV-related diseases, including multiple cancers and genital warts.
In the 15 years since its introduction, the vaccine has provided excellent protection against HPV and has delivered remarkable results – an estimated 90-per-cent reduction in cervical cancer rates among women aged 20–30.
The next frontier is achieving the elimination of cervical cancer – something once thought achievable only for infectious diseases – through widespread HPV vaccination and robust screening programmes.
By Dr Michelle Griffin (Director of MFG Health Consulting, clinical leader in the NHS and the World Health Organization)
11. Digital contraception
Non-hormonal digital contraception has revolutionised family planning by combining data-driven insights and user-friendly technology.
Apps like Natural Cycles and Clue empower women to track their menstrual cycles and use the data to prevent or achieve pregnancy, offering a convenient and accessible alternative to traditional contraceptives.
These apps utilise algorithms that analyse patterns in body temperature, ovulation cycles and other physiological markers, providing users with real-time predictions of the fertility window in their cycle.
This innovation marks a turning point in women’s health. In 2018, Natural Cycles became the first digital contraceptive to achieve US Food and Drug Administration (FDA) regulation, elevating the app to a regulated medical intervention.
Natural Cycles reports that the algorithm behind its app has a 93-per-cent success rate, the same as the contraceptive pill. MG
12. Tissue engineering
Going to the dentist and having a synthetic resin filling is fine, but it’s not as good as a real tooth. But what if we could grow real teeth in the lab from a person’s own stem cells and implant them back into their mouth?
This sounds like science fiction, but tissue engineering is a breakthrough technology that’s already being used to grow human tissue, through ‘scaffold technology’. Scaffolds are porous materials that support stem cells as they divide and grow into new tissues.
Artificial ears, trachea (windpipes) and bone have been grown this way and successfully implanted into human patients. Because the implanted tissues are grown from a patient’s own cells, there are no problems with immune rejection.
Artificial kidneys, knee cartilage and even hearts are also being grown this way, although these are still confined to lab experiments. No one can yet put a limit on this new technology, but the successful regrowing of teeth is on the horizon.
By Sir Mark Miodownik (Professor of Materials & Society, UCL; Author of It's a Gas: The Magnificent and Elusive Elements that Expand Our World)
13. Self-repairing materials
A modern smartphone contains half the elements in the periodic table and yet only has a lifespan of two to three years, on average. To save the massive amounts of energy we’re wasting on continually producing (and even recycling) phones and everything else that fills our lives, we need to find a new way of making products that last longer.
This is where the breakthrough technology of self-repairing materials comes in. Imagine a smartphone that can repair itself overnight when you plug it in.
Many different types of this technology are already on the market. Self-healing paints have room temperature fluidity, allowing them to flow back into cracks and fill the fissure when they form.
Self-repairing concrete for bridges and self-repairing asphalt for roads have already been deployed this century. Self-repairing electronics are coming to help us build a sustainable future. MM
14. Universal programmable chemical robots
What if any chemical reaction could be performed through code? This is what has become possible with the ground-breaking advancement known as chemical computation, or ‘chemputation’.
Chemputation combines automation, computation and modular hardware to transform chemical synthesis into a programmable, universal process. At its core is the ‘chemputer’ – a revolutionary platform capable of executing any feasible chemical synthesis.
It uses a concept known as ‘chempiling’, which translates chemical synthesis pathways into executable hardware configurations – basically acting as a chemical Turing machine. This process digitalises chemistry, increasing efficiency, accelerating research and reducing the risk of human error.
The integration of artificial intelligence into automated synthesis takes this innovation further, enhancing decision-making at every step of the process, from molecule design to reaction execution.
Because of this, chemputation is unlocking immense potential in drug discovery, material science and more.
By Prof Lee Cronin (Regius Professor of Chemistry, University of Glasgow)
15. Dark matter
The majority of the Universe is unseen, composed of two entities called dark matter and dark energy, and physics is currently unable to explain the origin of either.
Over the last 25 years, evidence for the existence of dark matter has become more compelling. Using gravitational effects to deduce where and how much of it there is, we’ve created maps that reveal a pervasive and invisible web.
The patterns seen in these maps, in the cosmic microwave background and in the distribution of galaxies, almost match our expectations for a dark Universe. But while 25 years of looking up has increased astronomers’ confidence, experimentation tells a different story.
After CERN’s 2012 detection of the Higgs boson, there were high hopes that the theoretical ‘lightest supersymmetric particle’ and favourite candidate for dark matter, would be discovered next.
Sadly, the elusive dark matter particle has yet to be found. The lack of detection means that we know what it’s not, even if we don’t yet know what it is. Scientists are working to build the most advanced detector yet, potentially in the UK.
Combined with upgrades at CERN and upcoming observations from the Euclid telescope and Vera Rubin Observatory, the hope is very much alive that it won’t be another 25 years before we understand the dark matter side of the Universe.
By Prof Catherine Heymans (Professor of Astrophysics at the Royal Observatory, University of Edinburgh; Author of The Dark Universe)
16. The Higgs boson particle
If we were to compare the most important discoveries in physics in the first quarter of the 21st century with those of the same period in the 20th, we might feel quite disheartened by the recent paucity of fundamental advances.
Maybe this is because we have largely uncovered the basic laws of the Universe.
It’s certainly hard to deny that those first two or three decades of the previous century were a golden age of physics, from the quantum revolution to Einstein’s two theories of relativity, to the structure of the atom with Ernest Rutherford.
But the theories and experimental discoveries over the past hundred years have still been remarkable, leading to deep insight into the fundamental building blocks of matter, potentially getting us closer to completing the jigsaw puzzle of reality.
One piece of the puzzle that had been missing ever since it was first proposed in the 1960s by Prof Peter Higgs (and others), was the Higgs boson. The particle was proposed as a manifestation of the Higgs field and the Higgs mechanism, explaining how elementary particles acquire mass.
Then, on 4 July 2012, experimental teams working with two giant particle detectors, ATLAS and CMS, at the Large Hadron Collider at CERN, announced they had finally observed the Higgs.
It was a landmark achievement in particle physics and a testament to technological innovation in ‘big science’, international collaboration and the human pursuit of knowledge.
It commanded global attention and captivated the wider public.
One might, of course, argue that the discovery of the Higgs wasn’t as profound as, say, the accelerating expansion of the Universe in 1998 (which therefore just misses out on this list), because physicists expected to find the Higgs. But it confirmed a critical component of the Standard Model of particle physics.
The Standard Model is an amalgamation of two separate quantum theories – the electroweak theory and quantum chromodynamics – which together describe the properties of all the known elementary particles and the forces acting between them.
Yet the Standard Model can’t be the final word because it doesn’t include gravity, doesn’t explain dark matter or dark energy, or where all the antimatter that should have been created at the Big Bang has gone.
Fifteen months after the discovery of the Higgs, in October 2013, the Physics Nobel Prize was awarded jointly to Prof François Englert and Prof Peter Higgs, “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles…”
It was awarded not for the experimental confirmation of the Higgs’ existence, but for the original theoretical prediction half a century earlier.
By Prof Jim Al-Khalili (Professor Emeritus in Physics, University of Surrey)
17. The James Webb Space Telescope
Launched aboard an Ariane-5 rocket on Christmas Day 2021, the James Webb Space Telescope (JWST) is nothing short of a technological marvel. Augmenting and improving on the role established by the Hubble Space Telescope, the JWST is designed for infrared astronomy in the wavelength range of 0.6-28.5 microns.
The JWST targets many important areas of astronomy and cosmology, from studying the first stars and initial galaxy formation, to spotting exoplanets and analysing their atmospheres.
A technologically and financially ambitious project, it hit many snags along the way to final deployment. The JWST’s large primary mirror was too large to be carried inside the rocket’s payload bay, for one.
The problem was solved by designing the mirror so that it could fold up for transit and open like the petals of a flower at its destination. That destination needed to be far from any bright radiation sources, such as Earth and the Moon, for JWST’s extremely sensitive infrared detectors to work.
Consequently, its base observation site is located 1.5 million kilometres from Earth, on the opposite side to the Sun. Fortunately, upon its arrival, JWST deployed without incident, which is just as well, because being so distant, there’s little we could have done to fix any problems.
In December 2022, JWST discovered the most distant, and therefore earliest, galaxies ever observed.
A galaxy survey project called JWST’s Advanced Deep Extragalactic Survey looked at an area where Hubble had recorded 10,000 galaxies, and detected a mind-blowing 100,000 galaxies in the same patch of sky.
It’s not just unfathomably distant objects that have had the JWST treatment, though. Jupiter, Saturn, Uranus and Neptune have all come under JWST’s scrutiny, and spectacular new details about each world have been revealed as a result.
As time goes on, JWST continues to break new ground and its observations are challenging existing theories about object evolution, posing many more questions along the way.
By Pete Lawrence (Astronomer and presenter of BBC Sky at Night)
18. Exoplanets
It makes the night sky far more interesting if we think of every star as being at the centre of a system of planets, like in our Solar System. Of special interest is the possibility that many of those planets are like Earth: the same size and at a distance to their parent star that allows water to exist. Could there be life on them?
Though they were officially discovered in about 1995, most of what we know about exoplanets has come in the last few years.
We’ve now detected over 5,000 of them, mainly with the ‘transit method.’ This is where you don’t actually detect any light from the planets, but the effects on the brightness of a parent star when a planet passes in front of it.
The most successful way we’ve carried out the transit method is by looking through the Kepler Space Telescope. Though the telescope has revealed a lot, it doesn’t tell us about what the surfaces of these planets are like.
For that, you’ve got to detect some light reflected from the planet. That’s much harder and, so far, has only been done for really big planets, not Earth-sized ones. The challenge for the coming 25 years is going to be detecting the light from the Earth-like planets orbiting nearby stars.
The James Webb Space Telescope may do some of this, but a giant ground-based telescope – the Extremely Large Telescope – is being built by a consortium of European countries in Chile. Its mirror is 39m (128ft) across, so it could collect a lot more light from faint objects than the Webb telescope, which is ‘only’ 6.6m (21ft) across.
There’s so much this new area of study could show us. I think if I were talking to a young person embarking on an astronomical career, I would advise focusing on exoplanets. The field is clearly going to be expanding and full of a high rate of discoveries in the coming decades.
By Lord Martin Rees (by Astronomer Royal, Emeritus Professor of Cosmology and Astrophysics, University of Cambridge)
19. Gravitational waves
Gravitational waves are significant for two reasons. Firstly, they’re an important physical phenomenon that tells us about the nature of gravity, confirming a further consequence of Einstein’s General Theory of Relativity. Secondly, detecting them has been an amazing technical achievement.
The Laser Interferometer Gravitational-Wave Observatory (LIGO) was a huge technical challenge because the expected amplitude of these waves is very small and must be detected at a vast distance. The effect you’re looking for is like the thickness of a hair at the distance of a nearby star. Quite amazing.
Many of us thought that LIGO wouldn’t find anything. Or, if it did, events would be fantastically rare, the instruments only being sensitive enough to detect collisions once a century or so.
But LIGO has been more successful than any of us expected, detecting a pair of black holes about 50 times the mass of the Sun crashing together within a short time of being switched on.
It was amazingly exciting and it’s now detecting about one or two such events a week. It’s worth celebrating for the hundreds of people who were involved with the set-up of these instruments.
The gravitational waves that LIGO observes are a short pulse of radiation of about 100 cycles per second, which is roughly the orbital period of two 50 solar-mass black holes when they merge together.
But there are far bigger black holes in the centres of galaxies with masses millions of times higher than LIGO can detect. Mergers of these are much rarer, but can be detectable out to greater distances.
The radiation produced, however, is at a much lower frequency. This has to be detected by instruments that, instead of having mirrors a few kilometres apart, has mirrors a few million kilometres apart.
The ESA-led Laser Interferometer Space Antenna (LISA) is planned to launch within the next 10 years. It should detect the rare mega-cataclysms when galaxies merge and the supermassive black holes in their centres collide. LMR
20. Psychedelic therapy
After much deliberation and campaigning from various interested parties, 2024 saw the United States Food and Drug Administration opt not to approve official use of MDMA-assisted therapy for post-traumatic stress disorder, citing insufficient evidence of the drug’s (commonly known as ecstasy) efficacy.
Despite this setback, it’s important to appreciate what a substantial breakthrough it is that we’ve even got to this point. While the benefits of psychedelics have a long history, the previous high-watermark of realising their potential therapeutic applications was in the 1950s and 1960s, when LSD use was widespread.
Unfortunately, a combination of LSD’s association with counterculture and President Richard Nixon’s ‘War on Drugs’, resulted in LSD – and psychedelics in general – falling victim to the brutal backlash. Their use was suppressed, both recreationally and in research contexts, for decades.
The loosening of the restrictions on research into psychedelics in the 21st century has produced potent and fast-acting treatments for depression, anxiety, obsessive-compulsive disorders, addiction and even sexual disorders.
It’s still early days for psychedelic therapies. Much of the research remains small-scale and short term, political and ideological barriers remain, and a mainstream rollout of psychedelic therapy would require significant investment.
Even so, especially with the relative stagnation in ‘traditional’ pharmacological interventions for mental health issues, this growing reassessment of the safety, potency and benefits of psychedelics could prove world-changing.
By Dr Dean Burnett (Neuroscientist and author; Author of Why Your Parents are Hung-Up on Your Phone and What to do About it)
21. Single-cell genomics
The human body is made up of almost 40 trillion cells and conventional wisdom suggests these are divided into about 200 cell types. Before the advent of single-cell genomics, our technologies studied cells in bulk, providing an average readout for thousands of cells without resolution of the individual cell identities.
In the human body, as in all multicellular organisms, there are different cell types within the same tissue that have distinct roles: muscle tissue contains subtypes of muscle cells, but also blood vessels, neurons, immune cells and more.
Without understanding this complexity, it’s impossible to determine how subpopulations of cells in different organs relate to each other and how they might be altered by disease.
In cancer, the DNA of a single cell mutates to allow it to multiply without control, leading to the formation of tumours. The tumour cells then interact with other cells in the microenvironment leading to the spread of the cancer.
Single-cell genomics has the power to resolve the individual cell types and cell states, revealing the pathways that promote tumour growth, allowing for the development of targeted therapy.
Another example is Crohn’s disease, where the comparison of healthy and diseased tissue at the single-cell level revealed the reason for a lack of response to therapy in some patients.
During the pandemic, single-cell genomics was used to determine which cells are susceptible to infection and later studies determined which organs are most affected and why. These are just a few of the applications of single-cell genomics and the list is expanding all the time.
More than 3,000 scientists around the globe are making a Human Cell Atlas (HCA) to provide a complete single-cell map of all the organs of the human body. This initiative has already led to a paradigm shift in the understanding of the function of normal cells and forms the basis for the understanding of the mechanisms leading to diseases.
The progress being made is leading to better diagnosis and treatment.
It has been less than a decade since single-cell analysis was developed and only six years since the HCA was launched. The next decade of single-cell genomics promises to be an even more exciting one.
By Dame Kay Davies (Dr Lee's Professor of Anatomy Emeritus, University of Oxford)
Read more:
- How to cut your dementia risk: 7 key lessons from the world's best studies
- How can I tell if I've got high cortisol levels?
- Scientists 'bring back' the woolly mammoth... as this mouse
22. CT scanning
A little over a century ago, palaeontologists in New York cut open the skull of a Tyrannosaurus rex, so they could see inside its brain cavity. It was a bold thing to do, as they had to destroy some of the priceless fossil. But they decided it was worth it, as it was the only way they could try to understand how this most iconic of dinosaurian beasts sensed its world.
Fast-forward to the turn of the millennium, when new technology rendered these destructive fossil surgeries obsolete.
In 2000, Prof Christopher Brochu published a scintillating study on the brain, intelligence and senses of T. rex. He didn’t use a saw; he used X-rays. Brochu put a fossil T. rex skull into a computed tomography (CT) scanner.
As the skull was the size of a bathtub, he needed to persuade engineers at Boeing to give him access to the machines they used to scan aeroplane engines to look for imperfections. Although huge, the scanner worked like one a doctor would use at a hospital, using a series of X-rays to build a three-dimensional digital model of the stuff inside the skull.
It revealed that T. rex had a big brain with enormous olfactory bulbs, which graced this iconic predator with a sharp sense of smell. Brochu’s study wasn’t the first CT scan of a fossil, but it made worldwide headlines and sparked a torrent of new research.
Suddenly everyone was putting their fossils in CT scanners. Today the procedure is so routine that many palaeontologists have scanners in their labs.
We use them for so many things: to identify hidden bits of fossils still encased in rock, or describe the microtexture and growth marks inside bones to understand how ancient organisms grew and metabolised. They can also help to make digital models that we can subject to computer simulations, testing how dinosaurs fed and moved.
To me, CT scanning is the biggest breakthrough in palaeontology over the last 25 years.
By Prof Steve Brusatte (Professor of Palaeontology and Evolution, University of Edinburgh; Author of The Rise and Fall of the Dinosaurs)
23. NASA's Curiosity Rover
In the kind of PR masterpiece we’ve come to expect from NASA, they didn’t play down the difficulty of landing their Curiosity rover on Mars. Instead, they called it their “seven minutes of terror” and explained that in those 420 seconds, it had to go from a speed of close to 21,000km/h (13,000mph) to zero in order to land safely on the planet’s surface.
When they achieved that, the mission’s place in history was all but secured, especially since they had used an innovative ‘sky crane’ landing system, which guided the rover to a much more precise landing than any previous planetary mission.
Then came the science.
Since 2012, Curiosity has made ground-breaking discoveries on Mars that help paint a more detailed picture of the planet’s past environment, its previous habitability and even its present ability to support life.
It found chemicals and minerals in Gale Crater that indicated the past presence of liquid water, clearly a pre-requisite for life. It then found various organic molecules that serve as the building blocks for life and can be used as food by microbial organisms.
While they don’t prove that life existed on the planet, they at least show that the correct molecules were present.
But perhaps the rover’s most tantalising discovery has been the detection of a seasonal release of methane from beneath the planet’s surface. Every Martian summer, the gas has welled up from Gale Crater.
While water-rock interactions could be responsible, scientists can’t rule out biological activity. The next generation of Mars rovers, such as ESA’s Rosalind Franklin will carry subsurface drills to investigate further.
Put together, Curiosity's longevity and its extraordinary scientific results significantly enhance our understanding of Mars, paving the way for future human missions and the search for extraterrestrial life.
To seal its place in 21st-century culture, Curiosity also took a selfie.
By Dr Stuart Clark (Astronomer, science journalist and author; Author of The Search for Earth's Twin)
24. NASA's DART mission
This entry made one of the biggest impacts both figuratively and literally. On 26 September 2022, NASA’s Double Asteroid Redirection Test (DART) mission smashed into the asteroid Dimorphos.
The collision destroyed the spacecraft completely and shifted the orbit of the asteroid – all on purpose. DART was a ground-breaking test of our ability to alter the orbit of a small asteroid, should we detect one on a collision course with Earth – and it succeeded spectacularly.
For the first time in history, humankind changed the trajectory of a celestial object and in so doing, proved a method for averting a natural disaster.
The asteroid in question was the smaller component of a double asteroid. The larger of the two is called Didymos. Originally discovered in 1996, Didymos is a chunk of rock with dimensions of roughly 851 x 848 x 620m (2,792 x 2,782 x 2,034ft).
Its companion, eventually named Dimorphos, was confirmed in 2003. With a dimension of just 177 x 174 x 116m (580 x 570 x 38ft), it was the perfect test subject for the mission.
Being locked into orbit around Didymos meant that the amount by which it had been moved would show up in a change of the time it took to circle the larger asteroid.
Before the impact, Dimorphos took just under 12 hours to orbit Didymos. After the impact, this time had decreased by just over half an hour, showcasing a viable method for deflecting potentially hazardous asteroids from Earth.
DART's accomplishments extend beyond planetary defence, though.
The mission has provided critical data on asteroid composition and impact mechanics, not to mention celestial navigation by hitting a 100m-wide (328ft) target at speeds of kilometres per second while having travelled millions of kilometres from Earth. SC
25. SpaceX's reusable rockets
For decades, the biggest roadblock to the exploration and utilisation of space has been the cost of launching objects and people into space.
The enormous Saturn V, used to transport astronauts to the Moon in the 1960s and 1970s, achieved a cost of around $5,000 (about £3,950) per kilogram lofted into space, but since the 1990s, smaller disposable rockets have only managed to achieve costs of around $10,000 (approx £7,900) per kilogram.
SpaceX has blown that figure out of the water and is currently in the process of revolutionising spaceflight. The game changer was the introduction of the Falcon 9 reusable rocket in 2015.
With a first stage booster that could return to Earth and land upright, the cost of launching people, supplies and technology into space started to tumble.
The reusability enabled more frequent launches, again expanding the range of commercial and scientific opportunities that space could offer. For example, it has made SpaceX’s Starlink project viable. This endeavour aims to fly thousands of smaller satellites in low-Earth orbit to provide unbreakable global internet coverage.
With Falcon 9, the cost of reaching orbit is around $2,000 (£1,500) per kilogram. The giant Starship rocket that SpaceX is now test-flying is estimated to slash the cost to an extraordinary $200 (£158) per kilogram.
SpaceX’s achievements have reshaped the global aerospace industry and mark a pivotal step toward humankind permanently extending its presence throughout the Solar System. But such progress doesn’t come without a cost.
The ability to launch so much into space threatens to dramatically increase the amount of space debris, which imperils working satellites and interferes with astronomical observations of the night sky.
Hence the innovation that these rockets allow must be understood in relation to the 'environmental damage’ that it could bring to Earth’s orbits and the night sky in general.
Nevertheless, SpaceX has brought us to a true watershed, not just in science but human history. SC
Read more: