A neutron is a very tiny piece inside an atom. Atoms are the small bits that make up everything around you — a chair, the air, your body. Inside an atom there are three even smaller pieces: protons, electrons, and neutrons. A proton has a plus charge, an electron has a minus charge, and a neutron has no charge at all. That is why it is called a neutron: it is ‘neutral’. Though actually, ‘no charge’ does not mean ‘not important’. Neutrons sit in the middle of the atom, in the nucleus, with the protons, and they help hold that middle together. If you take neutrons away or add too many, the atom can become unstable and even break apart. You will meet the word in science class, and in talk about nuclear power; you will not hear it much in everyday chat. The name was first used in 1899 by the physicist William Sutherland, but people did not all mean the same thing then — sometimes they were talking about what we now call a neutrino. The meaning we use today was set down again by Ernest Rutherford in 1920, next to the word proton.