Department of Biomedical Optics : This department's goal is the development and application of new optical methods for biomedical research. Biological function occurs often in a complex tissue environment and ultimately has to be studied in that context. Optical microscopy is virtually the only means by which living tissue can be studied with high spatial resolution. While the concept of optical microscopy per se is a rather dated one, going back several centuries, a number of developments over the last decades have several Lead to a return of the light microscope to the front-lines of biological research. Among those are the development of efficient non-toxic fluorophores together with highly sensitive means of fluorescence detection, optical sectioning microscopy, photochemical activation (uncaging) of signal substances, and the discovery and subsequent optimization of genetically encodable fluorophores (GFP and its variants).