MODEL RELEASED. Scanning electron microscope. Scientist positioning a sample in a scanning electron microscope (SEM, right). He is doing this remotely via the computer. A SEM uses an electron beam to obtain a three-dimensional image of an object. The beam is scanned over the sample in a vacuum, causing the emission of secondary electrons. These secondary electrons are detected and used to form an image that will be displayed on the screens. Photographed at the University of Newcastle Upon Tyne, UK.