Iridescence is the phenomenon that gives shining colours to the feathers of peacocks, hummingbirds, Morpho butterflies, mother-of-pearl in abalone shells and some flies. Iridescent colours change as you turn an object. The colours are not due to dyes, but rather are produced by a wide variety of intricate structures in di erent species. These structures were all unknown until the invention of the electron microscope. Explain why light microscopes cannot reveal them.