The lights have been turned on for the first time.
Nearly a century after Frits Zernike taught scientists to see the invisible by bending light, researchers at UC Berkeley have carried that same principle into the realm of electrons, building an instrument called Theia that can finally resolve the molecular structures that have long eluded science's sharpest tools. The breakthrough, sixteen years in the making, concentrates more power than a military laser onto a space smaller than a human hair, shifting electron beams with the same 90-degree phase trick that earned Zernike a Nobel Prize in 1953. What emerges is not merely a better microscope, but a potential key to the roughly 90 percent of human proteins whose structures remain poorly understood — and to the medicines that might one day depend on knowing them.
- Cryo-electron microscopy has long hit a wall with small molecules like hemoglobin, where faint scattering signals dissolve into noise before a clear image can form.
- The Theia system shatters that barrier by focusing 75 kilowatts of laser power — the brightest continuous point ever created — onto a space just microns wide to shift electron beam phase by 90 degrees.
- Early results are not incremental: Theia produced dramatically sharper images of hemoglobin, the field's benchmark for difficulty, validating 16 years of theoretical and experimental work in a matter of days after installation.
- The team is now pushing to sharpen Theia's focus further, a refinement that could double the structural data captured in a single image.
- The next frontier is cryo-electron tomography — imaging proteins not in isolation but inside living cells, in motion, as they actually function — a goal the laser phase plate may finally make achievable.
- Collaboration with Thermo Fisher Scientific aims to move the technology from a one-of-a-kind prototype toward instruments accessible to laboratories worldwide.
In 1930, Dutch physicist Frits Zernike discovered that light passing through a cell doesn't just dim — it also slows, shifting its wave in a way the eye cannot detect. By deliberately offsetting that phase, he could transform invisible cellular structures into visible contrast. The Nobel committee honored the insight in 1953, and phase-contrast microscopy became a pillar of biological research.
Nearly a century later, a team at UC Berkeley and Lawrence Berkeley National Laboratory has carried Zernike's principle into territory he could never have imagined. Their instrument, Theia, magnifies objects roughly 10,000 times more than a light microscope and can now image molecules that have long resisted visualization. The work, published in Science, is the product of more than 16 years of effort and opens a path toward understanding proteins that constitute roughly 90 percent of the human body.
The core problem is straightforward: electron microscopes struggle with small molecules. To avoid destroying delicate samples, scientists use a diffuse electron beam, but for molecules with fewer atoms this produces scattering patterns that blur into background noise. Hemoglobin — the oxygen-carrying protein in blood — sits near the lower limit of what conventional cryo-EM can handle, making it the field's standard benchmark. Physicist Holger Müller and his colleagues demonstrated Theia by imaging both aldolase, which conventional systems capture easily, and hemoglobin. The laser phase plate improved both, but the gain for hemoglobin was dramatic.
The collaboration began in 2010 when Müller joined forces with Robert Glaeser, a pioneer whose decades of cryo-EM advances were explicitly credited in the 2017 Nobel Prize in Chemistry. The engineering challenge was immense: they needed a laser powerful enough to shift an electron beam's phase by 90 degrees. The solution was to trap a laser in a mirrored cavity, bouncing it more than 10,000 times to concentrate 75 kilowatts onto a space just a few microns wide — the brightest continuous focal point ever created. After proving the concept on an older microscope, the team secured funding through the Chan Zuckerberg Biohub and acquired a custom-built Thermo Fisher instrument. Müller named the complete system Theia, after the Greek Titaness of light. Installation finished in 2025, and within days the team was producing images of striking clarity.
The work continues. Müller's team is refining Theia's focus — a step that could double the structural information per image — and expanding toward cryo-electron tomography, which assembles multiple angular views into three-dimensional reconstructions of proteins inside living cells. They are also working with Thermo Fisher to develop versions accessible to laboratories worldwide, translating a singular, hard-won prototype into a tool the broader scientific community can use.
In 1930, a Dutch physicist named Frits Zernicke made a discovery that would transform how scientists see inside living cells. He realized that light passing through a cell doesn't just lose brightness—it also slows down, shifting the timing of its wave in a way the human eye cannot detect. By deliberately shifting the non-scattered light by 90 degrees, he could turn that invisible phase shift into visible contrast, suddenly revealing cellular structures that had been too faint to study. The Nobel Prize committee recognized the breakthrough in 1953, and the phase-contrast microscope became a cornerstone of biological research.
Now, nearly a century later, a team at UC Berkeley and Lawrence Berkeley National Laboratory has adapted Zernicke's principle to a technology that operates at a scale he could never have imagined. They have built a laser-enhanced electron microscope called Theia that magnifies objects roughly 10,000 times more than a light microscope, and it can now capture images of molecules that have stubbornly resisted visualization. The work, published in Science, represents the culmination of more than 16 years of theoretical and experimental labor, and it opens a path toward understanding proteins that make up roughly 90 percent of the human body.
The challenge that drove this work is deceptively simple to state: electron microscopes struggle to image small molecules. To avoid destroying the delicate structures being studied, scientists use a diffuse electron beam—but for molecules with fewer atoms, this produces faint scattering patterns that blur into background noise. Hemoglobin, the protein that carries oxygen in blood, sits near the lower boundary of what current cryo-electron microscopy can handle. It has become a benchmark for the field, a test of whether a new system actually works. Holger Müller, a UC Berkeley physicist who led the development effort, and his colleagues demonstrated Theia's power by imaging both aldolase, a muscle protein that conventional systems capture relatively easily, and hemoglobin. The laser phase plate improved resolution in both cases, but the gain for hemoglobin was dramatic—proof that the technology addresses the field's most stubborn limitation.
The path to Theia began in 2010 when Müller and Robert Glaeser, a pioneer of cryo-electron microscopy, started collaborating on a laser-based phase plate. Glaeser had spent decades advancing cryo-EM since its invention in the 1960s, developing the protocol of freezing samples to liquid nitrogen temperatures to prevent beam damage and creating methods to combine thousands of images into detailed atomic models. His work was so foundational that the 2017 Nobel Prize in Chemistry for cryo-EM explicitly credited his contributions. But even with those advances, the field remained stuck on small molecules.
The first hurdle was engineering. Müller's team needed a laser powerful and focused enough to shift an electron beam's phase by 90 degrees—the same principle Zernicke had used with light, now applied to electrons. After a decade of research and development, they achieved it by trapping a laser beam in a mirrored cavity, bouncing it back and forth more than 10,000 times to intensify the focus. The result was 75 kilowatts of power concentrated on a space just a few microns across—more power than a military laser, focused to the brightest continuous point ever created. They proved the concept worked by installing the phase plate on an older Thermo Fisher Scientific microscope in Glaeser's lab. But the technology's full potential required a custom instrument designed from the ground up to work with the laser's capabilities.
In 2018, biophysicists from across the Bay Area gathered at a workshop hosted by the Chan Zuckerberg Biohub to see the team's progress. The response was immediate enthusiasm. With Biohub funding, the team acquired a new Thermo Fisher microscope tailored to the phase plate's specifications. Müller named the complete system Theia, after the ancient Greek Titaness of light and radiance. Installation finished in 2025, and within days, the scientists were producing images of striking clarity. The improvement was not incremental—it was transformative. Where conventional cryo-EM systems produce low-contrast images that require painstaking sample preparation and statistical averaging of thousands of molecules, Theia could capture clearer pictures even from lower-quality samples.
The work is not finished. Müller's team is now focused on sharpening Theia's focus further, a refinement that could double the structural information in each image. They are also working to expand the technology beyond single-particle analysis into cryo-electron tomography, a technique that assembles multiple angular views of a molecule into a three-dimensional reconstruction. Unlike single-particle cryo-EM, which requires isolated molecules, cryo-ET can image proteins in their native cellular environment—seeing them in context, in action, as they actually function. The challenge is that cells are messy, and the low signal-to-noise ratio of conventional electron microscopy makes interpreting those images difficult. The laser phase plate could change that, allowing biologists to see the proteome in motion for the first time.
Müller and his colleagues are also working with Thermo Fisher Scientific to develop user-friendly versions of the system for other laboratories around the world. The current prototype, he notes, is not street legal—it requires expert training and careful handling to maintain peak performance. But the collaboration aims to create streamlined configurations that preserve the technology's power while making it accessible to the broader scientific community. The breakthrough represents not just a technical achievement but a validation of sustained, collaborative research: more than 15 years of theoretical work, experimental refinement, expert machining, and institutional support converging on a single, transformative instrument.
Notable Quotes
Before, studying structures with cryo-EM was like trying to look at paintings in a dark gallery. With Theia, it's like the lights have been turned on for the first time.— Holger Müller, UC Berkeley physicist and lead developer
The laser phase plate has the potential to allow biologists to see and understand more of the proteome in action.— Jessie Zhang, postdoctoral researcher at UC Berkeley
The Hearth Conversation Another angle on the story
Why does imaging small proteins matter so much? What changes if we can suddenly see hemoglobin clearly?
Right now, about 90 percent of human proteins are too small for conventional cryo-EM to image well. That means we're essentially blind to most of the molecular machinery inside our cells. If we can see hemoglobin and proteins like it, we can understand how they fold, how they bind to drugs, how they malfunction in disease. That's the foundation for designing better medicines.
The laser they built sounds almost absurd—75 kilowatts focused to a few microns. How do you even contain that?
They trap it in a mirrored cavity and bounce it back and forth more than 10,000 times. Each bounce intensifies the focus. It's elegant, really—not brute force, but precision engineering. The brightness they achieved had never been done before.
This took 16 years. That's a long time to work on something with no guarantee it would work.
It is. But Müller and Glaeser had a clear theoretical foundation from 2010 onward. They knew what they were trying to do. The funding came from NIH, NSF, and eventually the Biohub. Institutions believed in the vision enough to sustain it.
What happens next? Is Theia the end point, or just the beginning?
It's the beginning. They're already working on cryo-electron tomography—imaging molecules inside cells in their native state, not isolated. That's a much harder problem, but with the phase plate, it becomes possible. And they're collaborating with Thermo Fisher to make versions other labs can actually use.
So this isn't just a Berkeley achievement. It's going to spread.
That's the hope. The prototype is optimized for peak performance, which means it's finicky. But the principle works. Once other groups have access to it, the pace of discovery could accelerate significantly.