A microscope is an optical instrument composed of one or several lenses. It can generate a magnified image of an object by physical means, magnifying tiny things to the extent that they are visible to human eyes. The earliest microscopes were manufactured in the fifteenth century, with the prototype being made of two lenses. Such invention marked the dawn of the era of cell-level research. The seventeenth to nineteenth century was the era of compound microscope; the nineteenth century of optical microscope; and the twentieth century being that of electron microscope. Optical microscopy is now widely used in surgery, especially in neurosurgery.