A wing that flashes like an oil slick is not always wearing color in the usual sense. On many insects, the so‑called pearly rainbows are produced by architecture, not dye: micro‑ and nano‑scale layers that turn incoming light into a precisely edited spectrum.Under a microscope, parts of these wings resemble engineered thin‑film coatings or even photonic crystals. Stacks of chitin and air, spaced a...More