[Kliment]

Try this, homemade electron microscope (appears to be WIP):

http://www.chemhacker.com/topics/stm/

Or this, a finished, working one:

http://sxm4.uni-muenster.de/introduction-en.html

[mechanical_fish]

These are STMs, by the way, not electron microscopes.

Making an electron microscope is probably a more expensive task for the homebrewer, because you invariably need a vacuum-proof chamber with a door that can be opened and closed, and the pumps to evacuate it...