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Indexed electron diffraction ring positions from a polycrystalline deposit identify candidate phases and give lattice parameters after camera-length calibration. Spot patterns from a small selected area establish zone axis directions, epitaxial orientation relationships or crystal twinning. Nanobeam mapping can reveal grain orientation changes, while systematic spot shifts can measure relative strain if lens distortions and scan drift are controlled. Spot or ring broadening can reflect finite coherent size, but also strain and instrumental broadening, so it is not an unqualified particle-diameter measurement. Use a calibration standard and an empty support region, vary dose to check electron beam damage, and combine spacing information with elemental analysis when chemically distinct phases have similar lattice parameters.