Cheating on physics gets us great microscopes and three Nobel Prizes

Standard fluorescence microscopy (left) and PALM images (right). Note that the scale bar in the far right image is roughly the diffraction limit.

Nobel Prizes/originally Betzig et. al., Science

This year's Nobel Prize in Chemistry honors an interesting mix of developments. It honors three researchers who overcame an apparent physical limitation in our ability to image microscopic objects, in the process building microscopes that are proving to be incredibly useful for biology. But because the breakthroughs depended in part on our understanding of the behavior of individual molecules, the prize comes in chemistry.

The limit in question is the diffraction limit, first described back in the 1800s by Ernst Abbe. This limit means that the best resolution we can obtain in imaging an object is half the wavelength of the light we're using to image it. If we're using visible wavelengths, this means we can't do much better than about 250nm—a distance that dwarfs viruses and individual proteins. Although lots of improvements in microscopy have been made since the 1800s, all of them kept running into diffraction-related problems.

At least, that was the case until recently. The Nobel Prize honors not one but two distinct ways of overcoming the limit. (Conveniently, we have coverage of both—see the sidebar.) In the case of one of the recipients, it honors an idea that came to him when he had given up on research and was working in the family business.