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.