Animation of the inner workings of a scanning electron microscope (SEM). The SEM uses a beam of electrons to image small objects, passing the tightly-focused beam in a raster pattern over the sample's surface. The electrons interact with the surface in different ways. Some of the electrons cause the emission of secondary electrons (SE) from the sample, which are picked up by detectors and used to build up an image of the surface based on the angle at which they are emitted. Some beam electrons are reflected, and detected as backscattered electrons. These can provide information about the composition of the sample. The device may also contain an X-ray detector, which picks up the X-rays emitted by the sample after the beam removes an inner electron from the sample's atoms. This is also useful in determining the composition of the sample.