Abstract: Many tropical rainforest plants under the low light exhibit a conspicuous blue iridescence on their leaves. The blue iridescence phenotype stems from the various same or different microstructures located in leaf epidermis. All kinds of microstructures are the products of adapting to low-light environment for growth and long-term evolution. The microstructures change the physical characteristics of the reflected light within plant tissue. They enhance light capture of photosynthetically important wavelengths and produce blue iridescence or composite color with periodic variation. The structural color also plays a key role in plant development. This review elaborates the formation mechanisms and biological functions of the structural color in plants.

Key words: low light environment, iridescent blue colour, structural colour, microstructure, physiological function, utility