The first good microscopes Greek mikrós, "small;" skopeos, "look at" were developed in the 17th century. Ordinary light microscopes consist of lenses that focus on an object, causing them to appear much larger than they are. Even then, the only microbes large enough to be seen through a microscope are bacteria and protozoa.

To see viruses, we must turn to the electron microscope. The electron microscope works the same way as the ordinary light microscope, with one major difference. Instead of using light to magnify an object, the electron microscope uses electrons. This allows very tiny objects like viruses to be seen.