Fluorescence and luminescence imaging provides submicron resolution not only of cellular constituents, but also of chemical dynamics within living cells. Further the response time provided by state of the art optical microscopes allows for visualization of local intracellular dynamics especially transient phenomena. With two-photon excitation techniques, the excitation light is generated directly inside the cell. This results in specificity and minimal cell damage since no light irradiation is used. The centerpiece of the facility is a Zeiss LSM510 confocal/multi photon excitation microscope. It is ideal for use with up to four different colored green fluorescent protein (GFP) mutants. A cell perfusion chamber is available for live cell studies (i.e. investigations of calcium pH, membrane potential) at both room and physiological temperatures. A second inverted confocal microscope, a Zeiss LSM410, is equipped with multiple lasers for efficient double and triple labeling. The confocal microscope is mainly used to look at immunofluoresence labeling by primary and secondary antibody techniques. In addition a third confocal, based on a fixed stage upright microscope is available. It uses water immersion optics that do not require a cover slip. This geometry allows imaging deep into intact tissue of living organisms. Imaging can be performed of mice in situ with concurrent blood sampling and infusions. The impact of a treatment on an organ can be visualized in real time.