Most colors on animals are produced by molecular pigments that absorb some wavelengths of visible light and reflect the others. But many of the most brilliant and vivid colors in nature are what are called “structural” colors. Like a rainbow, an opal, or an oil slick, structural colors are produced by optical interactions of light with biological nanostructures. Prum, an evolutionary ornithologist, and his collaborators are exploring the optical properties of these biological nanostructures; the self-assembly mechanisms that organisms use to grow them reliably; and the evolution of these structures for their functions in communication. The research draws not only on evolutionary biology and sexual selection, but also on optical physics, and materials science. And the data comes from such diverse sources as small-angle X-ray scattering and avian courtship displays among birds in the rainforests of New Guinea and the Amazon. Prum will put this all together for us (in under an hour!).