San Francisco start-up Huue uses bioengineered microbes to produce dye without toxic chemicals. First, Huue’s team studied how plants create indigo colour naturally in leaves. Then they spliced plant genes into bacteria. These bioengineered microbes mimic the plants’ chemistry and excrete indigo dye themselves. Huue says their dye is at least 5 times less toxic than standard indigo dyes and provides a sustainable method for making indigo dye that is compatible with existing manufacturing processes.