Electron Microscopy

Electron MIcroscopes come in two forms: The Tunneling Electron Microscope (TEM) and the Scanning Electron Microscope (SEM).

What is the difference? Both use beams of electrons.
However, the difference resides in the fact that the different types of machines direct the electron beam differently.

Tunneling Electron Microscopes send an electron beam *through* the object. This means theta they are good at gathering details on the inside of the object (which is especially important with cells), and of the surface of small objects.


Scanning Electorn Microscopes send their electron beams along the outside of objects. They are most effective for analyzing the surface of large/thick objects

The STEM (Scanning transmission electron microscope) combines some of the advantageous features of each, logically enough.

There are online simulators, based on Flash, Java, or the like, that give you an impression of how an electron microscope works. By adjusting settings common to an electorn microscope, and chosing from a premade set of 'samples', you see the resultant image.

http://micro.magnet.fsu.edu/primer/java/electronmicroscopy/magnify1/index.html is an example