The word microscope is a combination of two Greek words, mikros, or “small,” and skopos, or “watcher.” So microscope is a “watcher of the small!” It is an instrument used to see tiny things which are invisible to the naked eye closer it is brought to the human eye.

But when it is nearer than 25 centimeters, it is not clear. It is said to be out of focus. Now if a simple convex lens is placed between the eye and the object, the object can be brought nearer than 25 centimeters and still be in focus.

Today we describe this simply as using a magnifying glass. But ordinary magnifying glasses are really simple microscopes, and they have been used as such since remote times. So when we speak of the invention of the microscope, we really mean the “compound microscope.” In fact, today when we say “microscope,” that’s the only kind we mean.

What is a compound microscope? In this kind of microscope, magnification takes place in two stages. There is a lens called the “objective” which produces a primary magnified image. Then there is another lens called the “eyepiece,” or “ocular,” which magnifies that first image. In actual practice, there are several lenses used for both the objective and ocular, but the principle is that of two-stage magnification.

The compound microscope was invented some time between 1590 and 1610. While no one is quite sure who actually did it, the credit is usually given to Galileo. A Dutch scientist called Leeuwenhoek is sometimes called “the father of the microscope,” but that’s because of the many discoveries he made with the microscope.

Leeuwenhoek showed that weevils, fleas, and other minute creatures come from eggs and are not “spontaneously generated.” He was the first to see such microscopic forms of life as the protozoa and bacteria.

Today the microscope is important to man in almost every form of science and industry.