Observing proteins in their natural habitat: the living cell.

Fluorescence microscopy has played a tremendous role in uncovering the morphological features of cells and the expression pattern of proteins by immunofluorescence. Since the discovery of green-fluorescent proteins (GFPs), this technique has undergone a revival in the life sciences as the spatial distribution of ectopically expressed fusion proteins inside living cells can now be followed more easily. By further exploiting the photophysical properties of the emitted fluorescence with microspectroscopic methods, spatial information on the biochemical parameters of intracellular processes and reactions can be obtained. This possibility will not only play an important role in the understanding of biochemical reactions in signal processing and fidelity but also help to uncover the molecular mechanisms of organelle and cell morphogenesis.