All matter is made up of collections of tiny subatomic particles, protons, electrons, etc.
Each of these particles has a mass and a charge. By measuring a particle s mass and charge, scientists can determine what type of particle it is. In 1930, an English physicist named Paul Adrien Maurice Dirac suggested that for every particle there should be another particle with the same mass but with opposite charge. These particles are called antimatter. If a particle and its antiparticle ever contact with one another, they would both be destroyed and their mass turned into energy in the form of light.