A high time resolution electron microscope unit comprising a beam source for generating an exciting beam; a microscope for exposing the surface of a specimen to be observed to the exciting beam for emitting electrons from the surface; an image formation device for receiving the emitted electrons and for displaying an image representative of variations in the surface of the specimen; a gate mechanism for controlling the flow of emitted electrons from the specimen toward the image formation device; deflecting plates for deflecting the emitted electrons from the gate mechanism onto the image formation device; and a drive circuit for synchronizing the operation of the gate mechanism, the deflecting coil and the beam source.