Scanning Electron Microscopy uses a focused electron beam to scan solid samples. Secondary electrons are emitted from the sample and collected to create an area map of the secondary emissions. Since the intensity of secondary emission is dependent on local morphology, the area map is a magnified image of the sample. Spatial resolution is as high as 1 nanometer for some instruments, but 4 nm is typical for most. Backscattered electrons (BSE) and characteristic X-rays are also generated by the scanning beam and many instruments employ these signals for compositional analysis of the sample.