Researchers from Harvard University in Cambridge, Mass., have developed a technique that can be used to visualize neuron connections by genetically labeling neurons with multiple colors of fluorescent proteins.The method works much like televisions in that three colors (such as red, green and blue) can be combined to produce many different colors. The Harvard group’s technique produced a reconstruction containing approx-imately 90 colors, showing hundreds of neighboring axons in one small part of a mouse brain.Shown on the left are the cortex and hippocampus (a-d), with b and d showing higher magnification of the boxed regions in a and c. Motor axon terminals in a skeletal muscle are shown in e. In a-d, scale bars equal 50 μm, and in e, 10 μm. Images reprinted from Nature with permission of the researchers.