Electrons accelerated to a few hundred kilovolts will produce many signals when interacting with a thin specimen. A transmission electron microscope (TEM) can detect and analyze these signals to obtain images, diffractions and different spectra from an area of hundreds down to a few nanometers at atomic resolution. The images and diffractions can be obtained through a conventional TEM mode, where a parallel electron beam illuminates the interested area, or through a scanning TEM (STEM) mode, where a focused beam is scanned across the specimen. Two important signals used for chemical analysis are the characteristic X-ray and energy-loss electrons. STEM has good spatial resolution, which makes the microscope and its attached spectrometers a powerful instrument in
investigating the structure and chemistry of nanomaterials.