Compound Microscope is a tool that can be used for many purposes. From medical research to a day at the beach, your curiosity is limited only by your imagination. As with all disciplines, it is best to learn the basics and to apply them each time you use the microscope. A light source illuminates the object to be seen. That source can be a mirror, or the instrument can be self-illuminating. As light passes through the object, the lens nearest the object, called the objective lens, produces an enlarged image of the object in the primary image angle. The lens that you look into, the eyepiece, acts as a magnifier and produces an enlarged image of the image produced by the objective lens. To ascertain magnification, simply multiply the eyepiece magnification, usually 10X, by the magnification of the objective lens, usually 4x, 10X, 40X and 100X.