How the light-sensitive part of the biomolecule phytochrome changes from a light-adapted state to a dark-adapted state has been investigated by researchers at Ruhr-Universität Bochum and Philipps-Universität Marburg. So far, the structures of only a few light-sensitive biomolecules are known – and only for the final states in light and darkness, but not for the intermediate steps. Using various spectroscopic methods, the Bochum-Marburg team has now succeeded in gaining new insights into dynamic structural changes.