Electron microscopes use an electron beam to illuminate a specimen and can produce a magnified image 500,000 times its normal size. The two main types of electron microscopes are scanning electron microscopes (SEM) and transmission electron microscopes (TEM). Scanning electron microscopes produce images of a sample by scanning it with a focused beam of electrons, producing signals that can be detected and that contain information about the sample's surface topography and composition. Transmission electron microscopy transmits a beam of electrons through an ultra-thin specimen, interacting with the specimen as it passes through, forming an image from the interaction. These microscopes are used in clinical, research, forensic, and industrial laboratories for applications such as cell surface imaging, trace evidence analysis and single particle analysis. These microscopes require considerable investment, so look for superior technical support, extensive warranties and service contracts.