How does a scanning electron microscope create three-dimensional-looking images?

A scanning electron microscope (SEM) creates images with a three-dimensional appearance by scanning a focused beam of electrons in a regular pattern across the surface of a solid specimen.12

As the electron beam strikes the specimen, it stimulates the emission of high-energy backscattered electrons and low-energy secondary electrons from the surface. These emitted electrons are collected and used to modulate the intensity of a signal that builds an image, similar to how a television screen functions. Because the beam interacts with the topography of the surface—where different angles and features affect the number of electrons reaching the detector—the resulting image provides a sense of depth and relief, giving it a three-dimensional quality.12

This process allows researchers to study the surface structure of objects in great detail without requiring the thin sectioning necessary for transmission electron microscopy.13