As researchers look for sustainable alternatives to fossil fuels, one focus is clean-burning hydrogen. Hydrogen is often produced through steam methane reforming and electrolysis of water—energy-intensive processes associated with production of greenhouse gases. A climate-neutral approach needs to be based on renewable energy like sunlight. In the past, researchers have coupled photosystems or photosensitizers with hydrogen-producing catalysts in various ways, but now two separate groups report managing this feat in living systems, paving the way for organisms to produce hydrogen sustainably for as long as the cells stay alive. At Kiel University, Kirstin Gutekunst and colleagues genetically fused a hydrogenase enzyme to part of the photosynthetic machinery called photosystem I (PSI) in a Synechocystis cyanobacterium (Nat. Energy 2020, DOI: 10.1038/s41560-020-0609-6). Separately, Iftach Yacoby of Tel Aviv University and Kevin Redding of Arizona State University led a team that did something similar in Chlamydomonas reinhardtii (Energy Environ. Sci. 2020, DOI: 10.1039/c9ee03859k). Researchers say these studies lay important groundwork for developing living systems that can produce useful chemicals from light.