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Iridescent colours have been observed to be reflected from specially designed droplets of colourless liquids, with the reflected colour depending on the viewing angle. The finding reveals a curious mechanism for creating coloration.
Humans have been searching for better ways of making colours for centuries, frequently turning to nature for inspiration. The earliest colours used in art and clothing were naturally occurring pigments and dyes, which selectively absorb certain wavelengths of visible light. By contrast, the complex colours found in butterfly wings and mother-of-pearl are produced not only from pigmentation, but also by the scattering of light from microscopic structures whose sizes are roughly the same as the wavelengths of visible light — an effect known as structural coloration. In a paper in Nature, Goodling et al.1 describe another method for achieving brilliant colours that is based on the scattering of light from small droplets. This phenomenon parallels some of the most beautiful displays of colour found in the sky.