TauMap^® offers non-invasive in vivo three-dimensional mapping of fluorescence decay times in cells with submicron spatial and 50 ps / 250 ps temporal resolution even in tissue depths of 200 μm. The system enables scientists to observe living cells and even single organelles. The use of FLIM technology allows research on molecular and protein interactions as well as signalling cascades in single cells or between cells in a tissue. Fluorescence kinetics are a characteristic parameter which can be used to distinguish different fluorophores. TauMap^® opens the possibility for high resolution in situ 3D drug monitoring by non-invasive FLIM technology. The fluorescence decay time (τ) of a fluorophore depends on its local environment. Since the lifetime is often independent of the concentration, FLIM is a direct indicator of binding effects and energy transfers overcoming respective problems faced in fluorescence intensity measurements. The high temporal resolution of the TCSPC unit enables TauMap^® to study fluorescence resonant energy transfer (FRET, FLIM-FRET) without phototoxic reactions, which can be used for research on intracellular protein-protein interactions. By connecting a spectral imaging device to TauMap® additional information on the spectral distribution per pixel can be obtained (5D imaging).