As shown by Dong-po Song and his research team at Tianjin University, polyester-block-poly(ethylene glycol) bottlebrush block copolymers with varied side chain lengths can be used for the fabrication of biodegradable photonic microspheres and may be substitutes to nondegradable microbeads and toxic pigments in cosmetics. The pigment is made from biodegradable polyester materials such as polylactic acid. The nanostructure inside the new pigment is an “opal structure” that can form structural colors like butterfly wings or peacock feathers. It has characteristics of lasting beauty and changing color. By adjusting the angle of light, different colors can be reflected, creating a color change effect not seen in conventional pigments.