Electron microscopy has been fighting for a long time to give real access to surface information. SEM and TEM are, due to the high kinetic energies of the electrons and the excitation processes in the materials, not surface sensitive.
With the invention of Photoelectron Emission Microscopy (PEEM) by Ernst Brüche in the 1930s and Low Energy Electron Microscopy (LEEM) by Ernst Bauer in the 1960s true surface sensitive electron microscopy has become possible with a lateral resolution in the nanometer range.
With instruments like FE-LEEM/PEEM P90, developed by Ruud Tromp at IBM, that also includes generically an energy filter for spectromicroscopy and that can be equipped with an aberration correction in order to improve the resolution towards 1-2 nm, an uncomparable instrument is available for nanostructure characterization. A special version of this instrument is available also utilizing NAP-environments in the FE-LEEM/PEEM P90 in order to study reactivity of nanostructures in pressure up to 1 mbar. This technique is named NAP-LEEM and NAP-PEEM.