The metallic blue coloration of the Morpho Rhetenor butterfly is due to the microstructure of its wings. The wing scales have a fine periodic structure that acts like a photonic crystal (diffraction grating) to incoming white light. This structure effectively filters the white light and only strongly reflects the blue component. This is an example of biomimetics, where Nature leads the way in elegantly solving problems in optics and mechanics that we can incorporate into everyday products.
