using a complex genetic engineering technique, scientists have devised a way to label neighboring neurons in different colors, making it easier to differentiate and trace their connections. Called Brainbow for the stunning rainbow-like images it creates, the technique introduces a random mix of red, green, and yellow fluorescent proteins into each neuron. As artists know, combinations of these colors can produce over 100 different hues. Because each neuron gets its own color combination, researchers can better map their connections.