The optical reflectance of butterfly wings often shows peculiar features, their Bidirectional Reflectance Distribution Function (BRDF) is different from that of simple matt "painted" surfaces, e.g. butterfly wings often have a shiny, metallic appearance, The specific BRDF features are produced by constructive and destructive interference of the electromagnetic waves scattered on the optical nanostructures inside the scales covering the butterfly wing. Colors produced by this mechanism are called "structural colors", or "physical colors" -- in contrast to "pigmentary colors" or "chemical colors" produced by pigments. The angle dependent optical spectrum of the wing is a result of the complex interplay of several factors, including the photonic nanostructure inside the scales, absorbing pigments, and the geometrical arrangement of the scales. We can study the material and geometrical structure of the wing by microscopic techniques (light and electron microscopy) and measure its angle dependent optical spectrum. The aim of the PhD work is to establish a link between the geometrical structure and the optical properties. Calculations will be performed utilizing several methods, including Finite Difference Time Domain (FDTD), Finite Element (FEM) calculations, and ray tracing methods. Understanding the connection betwwen the wing structure and optical properties provides an important contribution to biology and makes it possible to design novel bioinspired optical devices. www.nanotechnology.hu