People sometimes ask Mats Gustafsson why there's been such a renaissance in light microscopy in recent years. His response makes it clear that he is not talking about your father's microscope.
"The catalyzing event was that computer power became easily available," he says. "Once you add a computer between the microscope and the human observer, the whole game changes." At that point, he says, a microscope is no longer a device that has to generate a directly interpretable image. Now it's a device to record information. Then a computer can extract that information and display it in a way that humans can understand. "In the methods that I work on, a common theme is that the raw images look like garbage. There is a lot of information there, but it is hard to make sense of with your eyes."
Optical microscopes—the kind that use light and glass lenses—have been around since the late 1500s. Although ideal for looking at live samples, these scopes all run up against the same wall: they cannot distinguish objects that are closer to each other than about 200 nm—a 500th of the width of a human hair. That may sound small, but the complicated molecular machinery inside cells is much smaller still. The basic problem is that light is a wave: the microscope runs into trouble when the objects of interest are smaller than the wavelength of the light.
About a decade ago, researchers started questioning this limit. This has resulted in several innovative techniques, all with cryptic acronyms: SWFM, 4Pi, STED, SIM, STORM, and PALM, to name a few. Under the appropriate conditions for each technique, these new microscopes can provide up to ten times better resolution than conventional light microscopes.
When Gustafsson started as a postdoctoral fellow at the University of California, San Francisco (UCSF), he had no formal optics background. When it came to trying to make a better microscope, this gave him, he says, "my own strange perspective on things. For example, I like to think in frequency space, rather than in real space."
One concept Gustafsson ended up working on is called structured-illumination microscopy, or SIM. The technology takes advantage of moiré patterns, which are produced by overlaying one pattern with another. Two rows of chain-link fencing seen from a distance can produce a moiré pattern, as can overlapping layers of gauzy curtains. Moiré patterns can be quite noticeable, even distracting, in digital photographs or on television: They are the reason that TV newscasters are told to avoid jackets with certain designs, such as hounds tooth.
In structured-illumination microscopy, the sample under the lens is observed while it is illuminated by a pattern of light (more like a bar code than the light from a lamp). Several different light patterns are applied, and the resulting moiré patterns are captured each time by a digital camera. Computer software then extracts the information in the moiré images and translates it into a three-dimensional, high-resolution reconstruction. The basic idea has been around since the 1960s, but wasn't fully realized until recently. In 2008, for example, Gustafsson and others used three-dimensional SIM to see parts of an animal-cell nucleus that had previously only been seen using electron microscopes (which can't distinguish colors, see deep inside cells and tissues, or provide images of living samples).
While at UCSF, Gustafsson also started working on developing a microscope with two lenses that would shine lights on a sample from two sides. The light is collected from both lenses and runs through a single detector linked to a computer. Gustafsson dubbed the method I5M. It can distinguish objects that are less than 100 nm apart, about 500 times smaller than the average diameter of a cell.
"We originally thought of structured illumination as a further improvement to I5M—we call this combination I5S," he says. "But we were surprised by how powerful structured illumination could be with a single lens, and since SI can be done with a much simpler microscope and on a wider range of samples than I5S, it has become an important method on its own."
After a combined degree in applied physics and electrical engineering in his native Sweden, Gustafsson wanted to learn "more fundamental physics than I could at engineering school." A one-year stint at the University of California, Berkeley on a Fulbright scholarship turned into more years, and a doctoral degree.
At Berkeley, Gustafsson had a brief foray into quantum field theory—because, he says, "If, like a child, you ask 'Why?' about something and respond to each answer with another 'Why?', you eventually end up at quantum field theory." He soon realized, however, that "the interesting basic questions in that field are extremely hard and may never be answered, and to survive as a scientist you have to work on answerable questions."
He then began working in microscopy. "I have been interested in biology since I was a child, but my skill set is better suited for physical sciences," he says. "Microscopy is a great way to use the physics to enable biology."
Gustafsson looks forward to interacting with other researchers at HHMI's Janelia Farm Research Campus, in both microscopy and other fields. "Imaging technology development relies entirely on close contact with biologists who have applications for it," he says. "The combined focus on imaging technology and neural circuits at Janelia provides some very interesting opportunities for collaboration."
As a kid, Gustafsson was a self-described "nerd" who co-founded his high school's science club and competed in the Math Olympiad. When asked why he does what he does, he describes the mysteries of the world in a unique way. "Suppose you lived in a world in which the ground was a crossword puzzle. Would you or would you not try to solve the puzzle?"
He pauses. "I can't imagine not trying. That's why I'm in science. Because we do live in a world like that."
