Electron microscopes have a high resolving power to reveal the details of the micro world and are used to investigate the ultrastructure of a wide range of biological specimens. However, they were long believed to not suitable for imaging biological specimens to achieve high resolution structures, because the powerful electron beam would destroy biological material and some other challenges, until the advent of cryo-electron microscopy. In this paper, we briefly reviewed the history and methodological development of electron microscopy and cryo-electron microscopy in biological specimens.