English: a) A motor nerve innervating ear muscle. b) An axon tract in the brainstem. c) The hippocampal dentate gyrus. In the Brainbow mice from which these images were taken, up to ~160 colours were observed as a result of the co-integration of several tandem copies of the transgene into the mouse genome and the independent recombination of each by Cre recombinase. The images were obtained by the superposition of separate red, green and blue channels. From Lichtman and Sanes, 2008