Andrew Chang, age 12, of Nackawic, New Brunswick, Canada, for his question:

WHAT IS AN ELECTRON MICROSCOPE?

An electron microscope is a device that uses a beam of electrons instead of light rays to magnify objects. The equipment is used by scientists who can easily see such tiny things as viruses and bacteria.

First pictures of individual atoms were taken with an electron microscope in 1970. The first microscope of this type was developed in 1931. Today they can be found in research labs and hospitals in all parts of the world.

There are two kinds of electron microscopes: transmission and scanning. A scanning electron microscope produces a magnified picture of the specimen on a television screen. Most powerful is the transmission electron microscope.