  *To be published in Springer Handbook of Surface Science (Springer Verlag)
[Preprint]*
  The capability to display images containing chemical, magnetic and structural
information and to perform spectroscopy and diffraction from a {\mu}m-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,
LEEM/PEEM systems are currently employed to study model systems in the fields
of nanotechnology, nanomagnetism, material science, catalysis, energy storage,
thin films and 2D materials. In the following chapter, we will present a brief
but complete review of this class of instruments. After an historical
digression in the introducing section, we will show first the basic operating
principles of a simple setup and then the elements that can be added to improve
the performances. Later, two sections will be dedicated to LEEM and 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 performances available nowadays.
Finally, a brief discussion about the future developments of cathode lens
electron microscopy will close the chapter.
