Indigo has been prized since antiquity for its vibrancy and deep blue hue and, for more than a century, its unique properties have been leveraged to produce the popular textile blue denim. However, the dyeing process requires chemical steps that are environmentally damaging. A team of researchers in the Molecular Biophysics and Integrated Bioimaging (MBIB) and Biological Systems and Engineering (BSE) Divisions, at JBEI, and UC Berkeley have developed a promising sustainable indigo dyeing process that relies on genetically engineered bacteria, mimicking the natural biochemical protecting group strategy employed by the Japanese indigo plant Polygonum tinctorium.