A Scanning Electron Microscope (SEM) is a powerful imaging tool that uses a focused beam of high-energy electrons, rather than light, to examine and analyze extremely small objects. Because electrons have much shorter wavelengths than light, SEMs can produce images at a much higher resolution than traditional optical microscopes. 

Inside an SEM, an electron source scans an object using an electron beam that is focused and directed towards a sample. Coils in the instrument move the beam back and forth in a precise raster pattern, scanning the entire surface. Samples placed in an SEM must be housed in a vacuum chamber. The vacuum prevents contamination and minimizes vibrations, all of which help improve the image quality and resolution. 

In addition to imaging, SEMs can be equipped with special detectors that provide valuable information. Secondary electron detectors (SED) reveal surface topography, backscattered electron detectors (BSD) help distinguish different chemical phases, and X-ray detectors identify which elements are present. Together, these capabilities allow SEMs to produce a high-definition image that details the elemental breakdown of a sample, including where an element is located and its approximate concentration.