Splashes of fuchsia, streaks of crimson and a smattering of taupe. When these dazzling displays of color—each hue denoting a different neuron—first appeared in the neuroscientific community in 2007, researchers hailed them as a novel way to understand brain structure. By inserting genes from bacteria, corals and jellyfish to code for three different fluorescent proteins into mouse nerve cells, Harvard University neuroscientists created neurons that would express a random combination of the proteins. These combinations could illuminate cells in up to 90 distinct colors, transforming scientific images into visually striking works of art.