You're looking at a "Brainbow," a microscope image of the nerve cells in a mouse's brain stem. It took first prize in this year's Olympus Bioscapes International Digital Imaging Competition.
Using a technique developed in Jeff Lichtman's laboratory at Harvard University, neurons in this image are colored by a combination of fluorescent proteins. The color allows scientists to trace each neuron's connections to other neurons, and eventually to build maps that will help them understand how the brain works.
Olympus received more than a thousand entries for the contest, which recognizes "the finest images of life science specimens captured through light microscopes, using any magnification and any brand of equipment." Among the other winners were a fruit fly testicle, rat tongue and chicken retina.—Dawn Stover