Fluorescence microscopy beyond the diffraction limit

In the recent past, a variety of fluorescence microscopy methods emerged that proved to bypass a fundamental limit in light microscopy, the diffraction barrier. Among diverse methods that provide subdiffraction spatial resolution, far-field microscopic techniques are in particular important as they can be operated in complex biological samples such as cells or tissue. Valuable new insights into biomolecular structure, organization and even dynamic processes in living cells have been gained with these novel microscopic techniques. In the present review, the most important concepts of far-field microscopy with subdiffraction resolution are introduced. The underlying physical concepts are discussed, and practical considerations for the application of these methods are made.