In the 1600s, Sir Isaac Newton and other scientists experimented with materials, light, and heat, and developed many basic laws of physics . By the early 1800s, the theory of the atom became popular. By the 1900s, scientists had discovered that atoms are themselves made of even smaller particles. This century research in particle physics has taken us deep into the heart of the atom, far beyond the limits of the most powerful conventional microscopes. Until very recently, there was no microscope powerful enough to see the 'building blocks' of matter.
Atoms are extremely small particles, out of which all matter is made.
They are the smallest particles of a chemical element that still have the properties of that element. A typical atom is about one millionth of a millimetre across - a million of them laid in a line would measure one millimetre across. The lightest atom is that of hydrogen , while one of the heaviest is that of uranium - about 200 times heavier than hydrogen. States of Matter Matter consists of atoms held together by electromagnetic forces. Plasmas are only found naturally in the coronae and cores of stars.