The Center for Advanced Imaging (CAi) at Heinrich Heine University provides state-of-the-art microscopy equipment for the in vivo analysis of membrane protein complexes in space and time. This includes systems for super-resolution fluorescence microscopy techniques like SIM (structured illumination microscopy), PALM (photoactivated localization microscopy) and STED microscopy (stimulated emission depletion), as well as confocal microscope systems with extensions for time correlated single photon counting (TCSPC) to detect simultaneously multiple fluorescence parameters with high sensitivity like in FLIM (fluorescence lifetime imaging microscopy) measurements. These fluorescence microscopic approaches are complemented by transmission and scanning electron microscopy to gain ultimate resolution. Furthermore, we are now starting to combine light and electron microscopy applications in one sample to further increase the information we can get. This will allow us to e.g., investigate quantitatively the signaling reactions across membranes and to analyze receptor complex compositions of different organisms under physiological conditions in cells and tissues. The final goal of this central project is to help to unravel general aspects of the functionality of membrane systems.