Microscopes allow people to look at objects that are too small to be seen by just the human eye. Scientists use microscopes to collect data for experiments or to examine samples, which are sometimes called specimens. Knowing the parts of the microscope helps scientists get the best possible view of their specimen.

At the top of the microscope are one or two tubes containing lenses; this is called the eyepiece. This is the part of the microscope scientists look through to see their specimen. The lens inside the eyepiece usually magnifies the specimen to 10 times its actual size. The eyepiece connects to a tube, at the end of which is another set of lenses called objective lenses. These lenses magnify the specimen further. Combined with the eyepiece, an objective lens with a power of 40x magnifies the specimen to 400 times its original size.

Scientists usually look at specimens mounted on pieces of glass called slides. The slides are clipped onto a flat area called a stage that is beneath the objective lenses. Under the stage is a light that shines upward and illuminates the specimen. Between the stage and the light are the aperture, which is a hole that can be made larger or smaller to let in more or less light, and the diaphragm, which directs light through the aperture.

The side of the microscope has two knobs that change the focus of the lenses so the specimen's image looks sharper in the eyepiece. The larger knob is the coarse focus, which moves the stage up and down, and brings the specimen in or out of focus. After the specimen is brought into the best focus possible using the coarse focus, the fine focus -- the smaller knob -- is used to fine-tune the image.

The bottom of the microscope is called the base. The microscope sits on its base, and the light is located on top of the base. An arm projects up from the back of the microscope's base. The focusing knobs are located toward the bottom of this arm, and the stage -- which is where the aperture, diaphragm and specimen are -- extends over the base from the arm. The eyepiece and objective lenses are located at the top of the arm over the stage and base. The arm acts as the microscope's handle. A microscope should be picked up by its arm, with your other hand supporting the base.