In the modern world of ever smaller devices and nanotechnology, electron crystallography emerges as the most important method capable of determining the structure of minute objects down to the size of individual atoms. Crystals of only a few millionths of a millimetre are studied. This is the first textbook explaining how this is done. Great attention is given to symmetry in crystals and how it manifests itself in electron microscpy and electron diffraction, and how this symmetry can be determined and taken advantage of in achieving improved electron microscopy images and solving crystal structures from electron diffraction patterns.