Question

magnetic focussing of an electron microscope

Answer 1

due to their negative charge, electrons can be concentrated by an electromagnetic field. As they pass through the sample and react with it depending of its characteristics, the electron beam is again scattered and sent to a detection chamber to register any difference of it to respect of its original configuration. Because the wave length of electrons is shorter than that of light, electron microscopes are so far at least 250X more powerful than optic ones.