Beyond doubt, nanobioscience represents one of the most innovative concepts in current basic and applied research. Technological advances provided the essentials for this ongoing scientific revolution, by making possible the observation, investigation and manipulation of biomaterials down to single molecules. Time-resolved single molecule detection has become the method of choice to characterize structural transitions between different functional states of isolated biomolecules. The development of ultra-sensitive detection schemes also has a strong impact on bioanalysis, as the sensitivity of biochemical assays could be dramatically increased. Whenever the available amount of sample is the limiting factor for unambiguous diagnosis e.g. in medical diagnostics, bioanalytics with single molecule sensitivity can be expected to become even an enabling technology. In this review, we describe methodological requirements for ultra- sensitive detection, and point out major advantages, in particular the novel information content.