Scanning electrochemical microscopy (SECM) is a type of scanning probe microscopy (SPM) where an electrochemical reaction at a microelectrode is used to generate information about an electrochemically (in)active surface in its immediate vicinity. Careful preparation and knowledge of the microelectrode response as well as the application of a suitable method enable the study of spatially resolved electrochemical kinetics or the electrocatalytic activity of any structure or material. In addition to a wide range of other applications, the method has become particularly well established in the research field of electrochemical energy storage and conversion.