Generally it is not sufficiently appreciated that electron microscopy is in fact a diffraction method. In essential aspects electron microscopes are more closely related to X-ray diffracto. meters than to light microscopes. In electron microscopes monochromatized radiation and coherent illumination (never used in light microscopy) correspond in X-ray diffractometers to the primary beam with a small divergence. Imaging ina general sense can take place in interference experiments between a primary beam and a scattered beam, or between diffe rent deflected scattered beams. This leads to the...