The components of a TEM are arranged in a long column with the electron-producing gun at the top. The electron beam generated by the electron gun passes down the column through a series of electromagnetic lenses, through the sample to an image collector at the bottom.

Schematic illustration of a TEM showing some components of interest.

On the way through the sample some parts of the material stop or deflect electrons more than other parts. The electrons are collected from below the sample onto a phosphorescent screen or through a camera. In the regions where electrons do not pass through the sample the image is dark. Where electrons are unscattered, the image is brighter, and there are a range of greys in between depending on the way the electrons interact with and are scattered by the sample.

There are many interactions between the beam and the specimen and some of these are shown in the diagram below. These are discussed in the SEM module.