According to About.com, the TEM microscope was co-invented in 1931 by Germans Ernst Ruska and Max Knoll. In 1986, Ruska received half of the Nobel Prize for Physics for his part in the invention.
A transmission electron microscope utilizes electrons by speeding them up inside a vacuum until their wavelength is only one hundred-thousandth that of white light. Beams focus in on a sample and are scattered or absorbed by the cell's parts in order to form the image. It is possible for a transmission electron microscope to view an object as small as the diameter of an atom. One drawback to transmission electron microscopes is that no living specimen can survive within their high vacuum, so these microscopes cannot be used to study the movements of a living cell.