In 1931, Ernst August Friedrich Ruska, while working at Siemens-Reiniger-Werke AG (precursor to present-day Siemens AG), built the first transmission electron microscope. Using electrons, which have a far shorter wavelength than light, it was possible to resolve individual objects at a far greater magnification. Four years later, Max Knoll discovered a means to sweep an electron beam over the surface of a sample, creating the first scanning electron microscope (SEM) images. In the ensuing 50 years the field has experienced both gradual progress as well as quantum leaps. Many of these milestones are laid out in the historical timeline presented in this poster. They accompany a primer on SEM, explaining the basics of the technology, the types of signals that can be detected, and how these are applied today in a research setting.