Butterfly wings are so synonymous with bold color that few people may wonder what makes them that way. But Yale University researchers studying the green color on the wings of five butterfly species say they have found the source of that striking color — three-dimensional crystals known as gyroids...

...The team surmised that the wing cells weave in and out among themselves, so that the external surfaces become internal, creating channels in which a material called chitin can be deposited. Chitin is the hard material that forms insect exoskeletons; when the cells die and decay, the chitin is left behind as a gyroid, making the wings a vivid green...

To read the article, click here, to see some gyroids, click here.