There are three large branches of microscopy: optical, electron and scanning probe microscopy. Optical and electron microscopy involve the diffraction, reflection or refraction of electromagnetic radiation or electron beams interacting with a specimen and the subsequent collection of this radiation to create an image. This process may be carried out by wide-field irradiation of the sample (for example, in standard light microscopy and transmission electron microscopy), or by scanning a fine beam over the sample (for example, in confocal laser scanning microscopy and scanning electron microscopy). In scanning probe microscopy, an image of an object's surface is created by a probe scanning the surface of the object of interest. An image of the surface is obtained by mechanically moving the probe in a raster scan of the specimen, line by line, and recording the probe-surface interaction as a function of the probe's position (coordinates).

The smallest size of objects that may be distinguished by a scanning probe microscope depends on the instrument's resolution, defined by the wavelength of the radiation used in the microscopy process and instrument distortions. The fundamental limitation lies in the fact that direct methods involving electromagnetic radiation do not make it possible to image an object that is smaller in size than the wavelength of radiation used. In scanning microscopy, resolution depends on the minimum size of the beam. In scanning probe microscopy, resolution depends on the size of the probe and the manner of its interaction with a specimen's surface.