Two of the most popular electron microscopy methods make use of scanning electron microscopes (SEM) and transmission electron microscopes (TEM).
The key difference between SEM imaging and TEM is that SEM produces an image by detecting secondary or backscattered electrons, whereas TEM uses transmitted electrons to form an image.
A relatively novel frontier in improving the depth of metrological data that electron microscopy can provide is three-dimensional (3D) electron microscopy.