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A backscattered electron is a primary beam electron redirected out through the incident side of a specimen after scattering. Backscattered signals commonly retain much more of the incident kinetic energy than emitted low-energy secondary electrons.^[ref]

In a scanning electron microscope, collecting these electrons can provide backscattered-electron atomic-number contrast, but specimen tilt, collection geometry and crystallographic electron channeling also change brightness. Comparing detector directions or tilting the specimen tests some of those contributions. A bright region is therefore not uniquely a region of greater atomic number.

Crystallographic electron channeling is orientation-dependent propagation of electrons in a crystal, where the spatially ordered electrostatic potential changes how the beam travels relative to atomic planes or columns. Changing crystal orientation can therefore change the collected signal even without changing chemical composition.

A small specimen tilt at fixed beam energy is a useful test: brightness changes correlated with orientation suggest a channeling or electron diffraction contribution. This matters when interpreting backscattered-electron atomic-number contrast or atomic-scale chemical maps. A bright region is not by itself proof of a different atomic number.