That rainbow you see on the ground when oil lies on the wet floor, that eye-catching swirl of colors shining on the outer surface of that bubble, or the sparkles of color on the back of your favorite CD; its iridescence and is present in several creatures in the animal kingdom. Iridescence is essentially the ability of objects to show different colors when viewed from different angles. When you look at the animal kingdom you see this property in many species of animals, insect exoskeletons along with bird feathers are the most common manifestation of iridescence, but fish scales and oyster shells also display an amazing range of colours. For the purposes of this article I will specifically look at the iridescences in the exoskeletons of the most diverse groups of insects on the planet, cockroaches (Order Cleopetra), and how this eye-catching pattern evolved to help them survive and thrive during evolution. if you want to find the origin of this beautiful metallic assortment of light you just have to look deep into these beetles, so to speak. Epidermal cells and even more specifically the smoother ER in these cells appear to be responsible. The smooth ER synthesizes proteins which then stack on top of each other to form an intricate lattice pattern. Differentiation in coloration in many animals results from a phenomenon known as thin film interference, using layer-on-layer structures with a lattice-like formation that interferes with visible light. Researchers know where these proteins come from, but they seem to assemble into this complex structure that provides a wide range of iridescent colors for no reason. Also, why did iridescence ever show up and thrive in the gene pool? All animals...... middle of paper ......and for cockroaches the beautiful iridescence are diffrection gratings. Diffraction is the scattering of light around an object or barrier. Diffraction gratings are parallel slits on the outside of the cockroach cuticle and when white light hits these grooves it is reflected, the different arrangement, spacing and thickness of the gratings can produce a range of colours. For this reason, Drifting gratings can create perhaps the most exceptional display of “rainbow-like colors.” The physics of light determines the order of color that will be visible on the beetle because it is the same order that the light spectrum falls in due to the very similar wavelengths to a rainbow. First red with the longest wavelength, moving on to orange, yellow, green, up to shorter wavelengths such as blue, then finally violet. Unlike three-dimensional photonic crystals, diffraction