The chapter provides an overview about superresolution microscopy techniques. We start out discussing the resolution limit and its origin and then review the principles of confocal microscopy in which the multiplication of illumination and detection point-spread function leads to enhanced resolution and contrast. Based on these concepts, resolution improvements due to nonlinear contrast mechanisms are discussed before introducing light-sheet microscopy with its superior axial resolution. The chapter proceeds by introducing structured illumination as a method to enhance the resolution in microscopy by optimizing the detectable bandwidth of spatial frequencies. Superresolution in microscopy is always based on prior information about the sample. In localization microscopy such prior information introduces additional dimensions to the spatial imaging problem, such as time or colour, that are then used to distinguish closely spaced single emitters. Several advanced superresolution microscopy techniques are discussed in that context, such as PALM and STORM as well as MINFLUX and SOFI. At the example of STED microscopy, we discuss how the nonlinearity associated with saturable transitions in conjunction with intensity zeros can in principle lead to unlimited spatial resolution.