The structural colours of animals have provided an attractive means of marketing for those reflectors designed and manufactured by humans. Over the past 30 years, optics well known to the physicist have emerged, example after example, in nature. But now the tables are turning and animals are becoming the first stage in the optical design process. Biologists and physicists have begun collaborative optics-based projects where the data will be supplied by nature. The real trigger of this surge in interest is the recent identification of 'photonic crystals' in animals. Animals, it would seem, have plenty to teach us, not only in terms of the design of their optical structures, but also their engineering. A familiar message, perhaps, except now action is underway.