An emission-electron microscope comprises an evacuated chamber with a superconducting magnet at one end generating a region of very high field strength. In this region a specimen is mounted and the surface of the specimen is irradiated with photons, typically x-ray or hard ultra-violet, from a source. As a result the specimen emits photo-electrons. The magnetic field is axially symmetrical along the length of the chamber and emitted electrons spiral about the lines of force traveling down the chamber into a region of lower magnetic field controlled by electro-magnet coils. Transverse kinetic energy of the electrons is converted into energy along the lines of force of the magnetic field and the divergence of the magnetic field lines causes electrons to produce on a detector an expanded electron image indicative of the distribution of electron flux across the surface region of the specimen. The emission-electrons may be produced by other stimulation methods, for example neutral atoms or heat (thermal electrons) and arrangements may be provided to permit only electrons of predetermined energy reaching the detector.