Microscopes magnify images so that we can see things that otherwise would be invisible with the naked eye. The most common type, light microscope, uses glass lenses to focus light and create a high resolution image. Some light microscopes collect light reflected from the surface of solid objects. Using stereo (twin) eyepieces, they produce a three-dimensional view of surfaces but usually don't reveal any internal structure. This type of instrument usually is limited to enlargements between 10 and a few hundred times. Large plant or animal cells are generally visible in at this magnification but smaller structures are mostly indistinguishable.

The microscopes most commonly used in biology laboratories transmit light through a thin specimen held on a glass slide. A condenser lens between the light source and the specimen increases illumination brightness while one or more objective lenses collects light passing through the specimen and forms an image. The...