One-dimensional structures, especially layered structures, are very common in nature, and in arthropods in particular. This is undoubtedly due to the very process of manufacturing the cuticle, by successive layers. With the same dimensionality, we also meet, although more rarely, structures in a network of lines. It is common to say that the former generate interference, the latter diffraction. Photonics encompasses the two phenomena under the same term: diffraction, but we will keep the common names and deal with interference for thin layers and diffraction for gratings in the context of wave optics (Fig. 9.1).