Stem cell differentiation—the process of turning a blank stem cell into a specific type of cell—can be regulated by controlling the reduction of stem cell metabolites, chemists at Scripps Research Institute have found (Nat. Chem. Biol., DOI: 10.1038/nchembio.364). Stem cells contain a pool of unsaturated molecules that decrease as stem cells mature. Oscar Yanes, Sheng Ding, and Gary Siuzdak discovered that they can inhibit differentiation by blocking certain enzymes that reduce highly oxidized metabolites in the pool. In addition, the researchers found they can expedite differentiation and obtain a greater number of mature cells by adding metabolites, such as the eicosanoid shown. Understanding the chemical basis for how stem cells mature opens the door for scientists to better manipulate differentiation to meet the different needs of patients who can benefit from stem cell therapies. For example, the Scripps team turned stem cells into neurons and cardiac cells, but Yanes says the process could work to control turning stem cells into any kind of mature cells.