Highly organised bacteria self-assemble to create structural colour that reflects light. The mechanism of colour generation is similar to the way the feathers of the peacock display vivid hues. There are no chemical pigments, the colour is created by light interacting with the ordered nanostructures created by highly aligned cells. This material is non-living but composed from sustainably grown, harmless bacteria that are then inactivated. Applications include cosmetics, paint and textiles. The colours are tunable and there is reflectivity in both the infra red and ultra violet. These materials are being developed for scalable production.