A transmission electron microscope (TEM) operates in a similar manner to an optical microscope, except that they use a beam of electrons to image the sample rather then a beam of light and they operate in a vacuum. TEM’s offer resolutions thousands of time better than optical microscopes, approaching atomic resolution thanks to the shorter wavelength. TEM analysis requires samples to be thinned down such that the electron beam can pass through them. It is a commonly used technique for metallurgical analysis.