The first electron microscope was made in 1932. This instrument was given its name because a beam of electrons are passed through the specimen rather than a beam of light. In an electron gun, the electron beam is produced in the hot tungsten filament. There are three main parts to the microscope which the beam must travel through. First, it passes through the microscope cylinder, then the spectrum chamber, and finally the image-recording system. Atmospheric pressure is not powerful enough to move the electrons very far, so the electron beam is in a vacuum. Living specimens could not survive the vacuum, and in turn cannot be studied under these microscopes.

The strength of electrons passing through the lens coil in the microscope cylinder determines the magnification. The image is formed by the atoms of the specimen. The atoms scatter the electrons creating dark and lighter areas spending on the atomic number. Finally, the image produced is either projected onto a fluorescent screen or recorded on film. The electron microscope is capable of magnification up to 50,000 times.

There are two main types of electron microscopes, the transmission electron microscope (TEM) and the scanning electron microscope (SEM). Both have an electron gun, a condenser, and objectives. The TEM is used to observe thin specimens because the electrons pass through it. The electrons pass through the objective lens to reach the specimen. Intermediate and projector lenses focus the electrons to form an electron image. The image-recording system then converts this image into one that can be seen by the human eye. When using shadow casting, the TEM produces a detailed, three-dimensional image. One uses this instrument to examine the internal structure of thin sections in cells and viruses.

The SEM uses a narrow beam of electrons to scan an object. Two types of electrons are emitted to scan the surface, backscattered and secondary. The backscattered travels in straight lines while the secondary move in curved paths. The secondary electrons give the fine detailing. The images produced by the SEM are three-dimensional. These are used to observe the exterior of cells.