T he world’s entire supply of opioid painkillers begins with the opium poppy (Papaver somniferum). Every year, about 100,000 ha of the crop is grown for its opiate compounds, which are extracted and converted into analgesics such as codeine and hydrocodone. Bioengineer Christina Smolke of Stanford University thinks it’s time for a new approach. Last year, she developed yeast that turns glucose into the opioids thebaine and hydrocodone. The work could offer a more efficient route to the vital drugs through industrial fermentation. Mark Peplow talked to Smolke about the promiseand the challengesof her synthetic biology project.