A microscope magnifies and resolves the image of an object that otherwise would be invisible to the naked eye. These objects include such items as human skin, the eye of a fly, cells of a living organism, viruses, individual molecules, and atoms.

The first optical microscopes, those that produce images through the use of visible light, used drops of water captured in a small hole to function as a magnifying lens. Later, magnifying glasses consisting of a single biconvex lens were developed and were capable of enlarging an object up to 20 times its original size as seen by the naked eye. (Scientists describe the power of magnification by writing a number followed by a times sign (x), so this would be expressed as 20x.)

Using several lenses in conjunction with each other is the secret of a microscope's success, however. Dutch spectacle maker, Zacharias Janssen, devised the first...