In photoelectron microscopy (PEM; also known as PEEM) ultraviolet light is used to liberate electrons from the surface of a specimen through the photoelectric effect. The emitted electrons (photoelectrons) have low kinetic energies (∼1 eV) and are accelerated by an electric field between the specimen and an anode, before being imaged by a lens system. The lens system forms the image of the specimen in parallel mode, as in TEM, rather than in scanning mode, as in SEM. Image contrast arises from differences in work function and from electric or magnetic fields over the specimen surface. Micro-fields associated with surface topography are also a source of contrast. Because of the low emission energies of the electrons PEM is a highly surface-specific technique and also is relatively non-destructive.

Several versions of the photoelectron microscope have been designed and constructed jointly by the University of Oregon (U0) and Portland State University (PSU), and the instrument has evolved to an advanced state of development.