The magnification that can be achieved in a scanning electron microscope depends on how narrow the beam of electrons that strikes the surface can be, and can reach 1 nanometer, about the size of 3 to 5 atoms. The control of the beam is achieved using magnetic fields, with other magnetic fields being used to shape the beam, and to move it across the sample. The range of magnification may range from 30x to as high as 500,000x.