A microscope is a very powerful magnifying glass. The entire world – our
bodies included – are made up of billions of tiny living things that are so
small you can't see them with just your eyes. But with a microscope, it's possible
to examine the cells of your body or a drop of blood. By using a microscope to see
these things up close, a doctor can spot cancer
cells, bacteria, and other problems
that could be causing a person's illness.