Biomembranes enclose biological cells like a skin. They also surround organelles that carry out important functions in metabolism and cell division. Scientists have long known in principle how biomembranes are built up, and also that water molecules play a role in maintaining the optimal distance between neighboring membranes—otherwise they could not fulfill their vital functions. Now, with the help of computer simulations, scientists of the Technische Universität München (TUM) and the Freie Universität Berlin have discovered two different mechanisms that prevent neighboring membrane surfaces from sticking together. Their results appear in the Proceedings of the National Academy of Sciences.