An electron microscope is a type of microscope that uses a beam of electrons to illuminate a specimen and create an image. Unlike light microscopes, which use visible light and lenses to magnify objects, electron microscopes can achieve much higher resolutions, allowing scientists to observe fine details at the nanometer scale, far beyond the capabilities of traditional optical microscopes.
Articles by others on the same topic
An electron microscope forms a spatially enlarged representation of a specimen using electrons, electron lenses, and a detector. Its appeal is access to structure too fine for an ordinary optical microscope, but a short de Broglie wavelength alone does not guarantee fine electron microscope resolution. Increasing magnification can enlarge an existing blur without revealing any additional structure.
In transmission electron microscopy, an electron gun illuminates a thin specimen; magnetic electron lenses form and enlarge its transmitted image on a fluorescent screen or detector. A vacuum reduces collisions with gas. Lens electric currents control focusing and magnification.[ref]
Transmission Electron Microscope (TEM) by JEOL. JEOL, The difference between Electron Beam and Light: gun, vacuum, magnetic lenses and screen
All of them need a vacuum because you can't shoot elecrons through air, as mentioned at Video "50,000,000x Magnification by AlphaPhoenix (2022)".