This site from Georgia State University Physics Department provides a discussion of how light refracts through the lenses of a microscope. Demonstrates the parts of a microscope and includes an interactive form in which the magnifying...

Microscope pioneer and amateur scientist Leeuwenhoek built a number of tiny microscopes with a variety of lenses.

This is an informative site from Georgia State University. It gives a discussion of the thin lens equation and an illustration of its use in determining the image distance based upon the object distance and the focal length.