A short review is given on scanning electrochemical microscopy (SECM). The historic background of the technique is briefly summarized and the basic principles outlined. The three different directions of its use: chemical microscopic imaging, the measuring of physicochemical constants and coefficients, and use as a micromachining tool are briefly discussed. The general built-up of the SECM apparatus is described. Preparation and use of several different measuring tips are introduced. A few examples are given of the application of SECM measurement in different studies.