Structural biologists have made important progress towards better understanding the functioning of the circadian clock. The circadian or inner clock coordinates the sleep-wake rhythm and many other body processes that regulate, for example, metabolism, blood pressure, and the immune system. A research team led by Professor Eva Wolf, recently appointed Professor of Structural Biology at the Institute of General Botany of Johannes Gutenberg University Mainz (JGU) and Adjunct Director at the Institute of Molecular Biology (IMB), has for the first time identified the molecular structure of a protein complex that plays an important role in regulating the circadian rhythm. At the same time, they also made a surprising discovery: The protein complex contains a zinc ion, which apparently stabilizes it. These results could form the basis for new strategies for treating illnesses that are the result of circadian clock dysfunction.