The capability to display images containing chemical, magnetic, and structural information and to perform spectroscopy and diffraction from a μm-sized area makes cathode lens electron microscopy one of the most used and reliable techniques to analyze surfaces at the mesoscale. Thanks to its versatility, LEEMlow-energyelectron microscopy (LEEM)/PEEM systems are currently employed to study model systems in the fields of nanotechnology, nanomagnetism, material science, catalysis, energy storage, thin films, and 2-D (two-dimensional) materials. In this chapter, we will present a brief but complete review of this class of instruments. After a historical digression in the introductory section, we will first show the basic operating principles of a simple setup and then the elements that can be added to improve performance. Later, two sections will be dedicated to LEEM and PEEMphotoelectronemission microscopy (PEEM), respectively. In both cases, a theoretical discussion on the contrast mechanisms will prelude to a showcase of the operating modes of the instrument, with clear examples that will show the best performance available today. Finally, a brief discussion about the future developments of cathode lens electron microscopy will close the chapter.
