Photosynthesis plays a crucial role in shaping and sustaining life on Earth, yet many aspects of the process remain a mystery. One such mystery is how photosystem II, a protein complex in plants, algae and cyanobacteria, harvests energy from sunlight and uses it to split water, producing the oxygen we breathe. Now researchers from the Department of Energy's Lawrence Berkeley National Laboratory and SLAC National Accelerator Laboratory, together with collaborators from Uppsala University and Humboldt University and other institutions have succeeded in cracking a key secret of photosystem II.