The emerging field of nano-science/nano technology has been driven by and requires the development of novel tools/techniques for observing at the nanoscale. A prominent tool for such studies with a highly non-invasive character is single molecule microscopy. Optical spectroscopy/microscopy at the ultimate limit of a single molecule has grown over the past decades into an extremely powerful technique for exploring the individual nano-scale behavior of molecules in situ and in real time in complex local environments. Observing a single molecule removes the usual ensemble average, allowing the exploration of hidden heterogeneity in complex condensed phases as well as direct observation of dynamic changes, without synchronization.

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