A transmission electron microscope can reach magnifications of up to 500,000 times that of a human eye and a thousand times the magnification of a compound microscope. The transmission electron microscope does not use a standard lens to complete its magnifications; instead, it uses a monochromatic beam of electrons passed through a magnetic field, which acts as a lens.
The specimens viewed in this type of microscope are extremely thin so that the electrons can interact with the item as they pass through it. The microscope can focus as small as a single column of atoms. These results are viewed either through a camera, normally a CCD type, a florescent screen or photographic film. The magnification on the microscope can be adjusted simply by changing the amount of current running through the coil or the lenses, depending on the setup of each particular microscope.
There are normally three lenses in a transmission electron microscope, which include the condenser, objective and projector lenses. The condenser creates the beam before moving into the objector lenses to bring it into the correct focus as it passes through the object being viewed. The projector beams, as the name suggests, process the image onto an imaging device like the CCD camera or photographic film.