Some objects are so small that our eyes cannot see them. We cannot see atoms or molecules, or the cells of our bodies, or viruses that carry disease. A microscope uses lenses to make tiny things appear bigger so we can see them clearly. There are two main kinds of microscope. Optical microscopes create a magnified image using light from an object. Electron microscopes are much more powerful and use a beam of electrons instead of light.

An optical microscope uses light. The object to be viewed is cut very thin so light will pass through it, then placed on a piece of glass called a slide. A mirror at the bottom gathers light and reflects it up through the slide. A system of lenses magnifies the object, making a bigger image that may be seen in the eyepiece at the top.