An artificial skin made with synthetic melanin nanoparticles would make chameleons green with envy were the lizards capable of such a petty emotion. The synthetic skin changes color faster than a chameleon’s, provided the humidity of the air surrounding the engineered film changes quickly enough (Chem. Mater. 2016, DOI: 10.1021/acs.chemmater.6b02127). Although the skin can switch its hue quicker than chameleons and other color-changers in nature, it was actually inspired by them, say the skin’s developers, led by Ali Dhinojwala of the University of Akron; Nathan C. Gianneschi of the University of California, San Diego; and Matthew D. Shawkey of the University of Ghent. Iridescent bird feathers, such as those found on tree swallows, reversibly change color with changes in humidity. Scientists believe this is a result of the swelling or shrinking of feather fibers as they take on or lose moisture, respectively. The artificial skin works faster but in much the same way, with stacks of nanoparticles made from polydopamine, a synthetic melanin, playing the role of the keratin structures. Films of the nanoparticles could therefore provide the basis for rapid and easy-to-read humidity sensors, the researchers say.