Single-molecule techniques impacted optics, electronics, biology, and chemistry.  In the biological sciences, the study of proteins and other complex biological machinery was limited to ensemble experiments that nearly made impossible the direct observation of their kinetics.  For example, it was only after single molecule fluorescence microscopy was used to study kinesin-myosin pairs in muscle tissue that direct observation of the walking mechanisms were understood.  These experiments, however, have for the most part been limited to in vitro studies, as useful techniques for live cell imaging have yet to be fully realized.  The promise of single molecule in vivo imaging, however, brings with it an enormous potential to directly observe bio-molecules in native processes.  These techniques are often targeted for studies involving low-copy proteins, many of which are still being discovered.  These techniques have also been extended to study areas of chemistry, including the mapping of heterogeneous surfaces.