Dr. Kiki creates a rudimentary microscope from scratch and breaks down how they actually work. (popSiren)
Learn more about the history of the microscope here: http://www.az-microscope.on.ca/history.htm
And if you want to build your own, you'll need the inside of a paper towel roll, some tin foil, an eyepiece and a lens. For parts, go to http://www.opticsplanet.net/microscope-accessories.html.
