Electron diffraction via the transmission electron microscope is a powerful method for characterizing the structure of materials, including perfect crystals and defect structures. The advantages of electron diffraction over other methods, e.g., x-ray or neutron, arise from the extremely short wavelength (≈2 pm), the strong atomic scattering, and the ability to examine tiny volumes of matter (≈10 nm3). The use of electron diffraction to solve crystallographic problems was pioneered in the Soviet Union by B. K. Vainshtein and his colleagues as early as the 1940s [1]. In the elektronograf, magnetic lenses were used to focus 50 keV to 100 keV electrons to obtain diffraction with scattering angles up to 3° to 5° and numerous structures of organic and inorganic substances were solved. The elektronograf is very similar to a modern transmission electron microscope (TEM), in which the scattered transmitted beams can be also recombined to form an image. As the result of numerous advances in optics and microscope design, modern TEMs are capable of a resolution of 1.65 Å for 300 kV (and below 1 Å for 1000 kV) electron energy-loss combined with chemical analysis (through x-ray energy and electron-loss energy spectroscopy) and a bright coherent field emission source of electrons. Routinely in TEM, selected area diffraction (SAED) has been used to obtain spot diffraction patterns from crystals. However, the volume that can be sampled using this technique is defined by the size of the aperture inserted in the image plane of the objective lens. This leads to an effective probe size of a few hundred nanometers, which makes SAED unsuitable for obtaining diffraction information from individual nanostructures, within a dense cluster of such structures. Improvements in spatial resolution have been achieved by limiting the area of illumination on the specimen. In TEM mode, a quasi-parallel nanobeam (TEM/nanobeam diffraction – NBD) or a convergent beam (TEM/convergent beam electron diffraction – CBED) may be produced on the specimen. The TEM/NBD technique enables the formation of spots in the diffraction pattern and subsequent easy indexing. The TEM/CBED method gives rise to discs at the diffraction plane. The convergent incidence of the beam may also result in dynamical effects, such as Kikuchi lines in the diffraction pattern. Electron backscatter diffraction (EBDS) is usually used with a SEM and can provide quantitative microstructural information about the crystallographic nature of most inorganic crystalline materials. A TEM technique similar to EBDS-SEM is ASTAR (NanoMEGAS) but has nanometer resolution. The technique utilizes Precession Electron Diffraction patterns [2] which can be obtained automatically and indexed via pattern identification software.