Electron diffraction offers considerable advantages over other methods for determining the structure of radiation-sensitive biological macromolecules such as proteins. On the one hand, structural determinations can be carried out with a fraction of the sample quantities required for other methods, which can represent a considerable cost saving in pharmaceutical screening experiments, for example. On the other hand, the positions of hydrogen atoms, which are highly relevant for the biological function of molecules, can be determined much more accurately than is possible with X-ray diffraction. For example, precise knowledge of the protonation states of proteins provides a much better understanding of how they work. While simple electron diffraction experiments with cryogenically cooled protein crystals can also be performed with laboratory-based equipment, we are developing a special measuring chamber for protein crystals at REGAE that allows proteins to be investigated with ED even in a non-frozen state at physiological temperatures.