colour as is seen in many Avian orders, is the product of coherent,rather than incoherent, scatter from the spatial variation in refractiveindex of medullary keratin in feather barbs or of collagen fibres in thedermis18.Photonics in floraAdvanced photonic development is not limited to fauna. Certainanomalous species of flora also show partial PBGs that underpin anoften vivid structural colour19 (Fig. 5a). Invariably this is mediated byvariations in 1D multilayering (although more complex structuraldesigns are also thought to exist), producing iridescence in vascularplant leaves, fruits and marine algae4. Periodicity is generally formedby laminations of hydrated cellulose, which are usually located close