Today, scientists can observe minute biological processes in realtime -- but that wasn't always so. Once, they were limited to looking at bacteria-sized objects as shapeless blobs. Electron microscopes can see more, but they require that samples be sliced and prepared -- so nothing living can be observed, especially not in motion.
The three men honored by today's Nobel Prize contributed to super-resolution fluorescence microscopy, which allows us to see everything from DNA transference in action to the changes that neurons go through as we learn something new.
Scientists used to believe that microscopes using light would never get past a certain threshold: Around half the wavelength of light, or .2 micrometers. Some organelles in human cells would be visible, but only just -- and most remained a mystery.
As a young upstart at Turku University, German scientist Stefan W. Hell decided to take on this supposedly unsolvable problem. He worked in a lab that studied fluorescence microscopy -- where glowing molecules are excited and made to attach to parts of a cell, lighting them up and making them detectable. But it was limited. In looking at DNA, scientists could see entangled strands of DNA, but not individual strands.
In 1994, Hell published his solution. His method, called stimulated emission depletion (STED), acts as a sort of focused flashlight. While one pulse of light excites all of the fluorescent molecules in the sample, a second pulse quiets the glow from all but a nanometre-sized section. The smaller each individual measurement is, the better the resolution of the total image when it's put together. In 2000, Hell demonstrated his STED microscope with the best shot of E. coli bacteria ever taken with a light microscope.
Meanwhile, Moerner was working on controlling the fluorescence of molecules. He discovered that by using specific wavelengths of light to activate them, one could keep green fluorescent molecules from just dying -- they could turn them on and off. A regular microscope could detect their glow, allowing researchers to distinguish individual molecules.
Inspired by his work, Betzig published some research on the subject, but soon left academia for his father's business. After many years of total estrangement from scientific research, he felt called back. In 2005, he published a breakthrough: Using fluorescent proteins that could be turned on and off at will, he created images of a resolution much higher than the theoretical limit. Weak pulses of light activate the proteins for a very short time, so that pieces of the subject can be illuminated bit by bit. These images are superimposed to form high-resolution images -- without killing the cells being observed, or even interrupting their biological processes. The single-molecule microscopy method is now widely used.
All three laureates continue to use their findings for practical research (as does the rest of the scientific world). Hell has studied nerve cells to understand how the human brain fires off information. Moerner has studied the proteins associated with Huntington's disease, and Betzig has watched cell division occur in embryos.