Abstract: The scanning transmission electron microscope (STEM) is one kind of transmission electron microscope. With the invention of the spherical aberration corrector, the resolution of STEM can reach sub-Ångstrom levels. High spatial resolution imaging and high energy resolution spectroscopy can be achieved simultaneously through the combination of STEM and electron energy loss spectroscopy (EELS). The fundamentals and application of STEM will be briefly introduced, with emphasis on the basics of high angle annular dark field imaging and its application in microstructural and chemical analyses. The characteristic features of EELS and its application in material science will also be discussed.