What do butterflies and solar cell research have in common? Both have been developing tiny crystals that selectively reflect colors. Over millions of years of evolution, butterfly wings have developed the tiny crystal nanostructures that give butterflies their vivid colors. At Argonne National Laboratory, scientists are working to manufacture these crystals, which could one day be used to create "greener" and more efficient paints, fiber optics and solar cells. In this photo, the iridescent scales of an emerald-patched Cattleheart butterfly are magnified 20 times to highlight the crystals that selectively reflect green colors. | Photo courtesy of Argonne National Laboratory.