Electron Microscopy is a technique that makes use of the interactions between a focused electron beam and the atoms composing the analyzed sample to generate an ultra-high magnification image. This technique, when compared to normal light microscopy, has the advantage of breaking the limit of resolution that comes with light microscopy and allows for resolution that can reach the atomic level.
Light microscopy is, in fact, limited by the wavelength of light, which is physically set in a defined range. When going below the lower limit of this range, the image becomes blurry and it is no longer possible to distinguish details.