"Brainbow" zebra fish.

Neurons are labeled in multiple colors with Brainbow fluorescence microscopy. Three fluorescent proteins (cyan, yellow and red) are randomly taken up by various neurons, offering a palette of dozens of colors to help scientists follow complex neural pathways. Shown here is a five-day-old zebra fish larva viewed from the dorsal side, captured using a 20X objective.

Image credit: Dr. Albert Pan, Harvard University, Cambridge, Mass., U.S.

(Source: scientificamerican.com)