Credit Liliana D'Alba. Minuscule packets of melanin sandwiched between the keratin of this African starling's feathers interact with light to produce brilliant iridescent color. These structures inspired the creation of new materials made of nanoparticles of synthetic melanin that create a range of pure hues depending on their structural arrangement. High resolution image at http://physicalsciences.edu/press/starling.jpg
Optical image of thin films of synthetic melanin nanoparticles. Hue varies with the thickness and packing density of the particles.
Scanning electron micrographs of films made from nanoparticles of polydopamine seen in cross section. The top film produced a red hue, the bottom green.