Not many of the rules of physics are actually set in stone, but the diffraction limit is one of them. In imaging terms, the limit determines the smallest discernable feature you can make out through a microscope. It’s etched on this memorial to the 19th century German physicist Ernst Abbe, located in Jena (right).
But as the Bible proves, rules set in stone are made for breaking, and yesterday we heard from two clever physicists who’d beaten the diffraction limit. W.E. Moerner of Stanford University in California looked at fluorescing proteins in cells with a very dim light. Each cell gave off a little pinprick which could then be pinpointed using computer software, and in this way, Moerner could perform in situ imaging of individual proteins. Stefan Hell of the Max Planck Institute for Biophysical Chemistry in Gottingen had another scheme: He used two superimposed beams of light to make sure that only the protein directly under his microscope lit up. Both of these methods were able to image molecules just nanometers in size.
Of course, they’re not the only ones—there are plenty of non-optical systems that can resolve nanometer scale features (scanning-tunneling microscopes for example). But the advantage of these systems is that they can provide in situ images of biological molecules. It’s all sexy enough that our sister pub, Nature Methods, named these and related techniques as its method of the year. Check out their cool video to learn more:
Image: S. Hell