Brainbows

Four years ago, Harvard scientists devised a way to make mouse neurons glow in a breathtaking array of colors, a technique dubbed “Brainbow.” This allowed scientists to trace neurons’ long arms, known as the dendrites and axons, through the brain with incredible ease, revealing a map of neuron connections.

Using a clever trick of genetic engineering, in which genes for three or more different fluorescent proteins were combined like paints to generate different hues, researchers created a system to make each neuron glow one of 100 different colors.

. . . . This is the first time that scientists have converted the technique to work in fruit flies, and because these organisms have a very sophisticated set of existing genetic tools, researchers can exert even greater control over when and where the fluorescent proteins are expressed . . . . Researchers have traditionally had to stain just one or two neurons in each sample, painstakingly compiling data from many brains to build a map.

More at technology review.