Atoms & Molecules

the long version

Everything in the universe is made up of tiny particles called atoms, which combine to make molecules. Elements, such as iron or nitrogen, are made up of a single kind of atom. Atoms of different elements can also join together to make a new substance. For example, a molecule of water is made up of two hydrogen atoms and one oxygen atom. Learn about the discoveries of physicists and chemists while you explore the invisible world of atoms and molecules.