Electron microscope is a device that uses a beam of electrons to magnify a specimen. Electron microscopes can resolve (give clear pictures of) features much smaller than those visible through optical microscopes. Optical microscopes use visible light and glass lenses to magnify images. Some electron microscopes can even resolve individual atoms. Electron microscopes serve as a major research tool in biology, chemistry, medicine, metallurgy, physics, and nanoscience, the study of extremely small things. Ernst Ruska and other German scientists built the first electron microscope in 1931.