Another kind of matter, known as antimatter, is also rarely seen in our world, though it plays a large role in the subatomic realm and is created in profusion in particle accelerators. Antimatter is like regular matter but opposite in electric charge and certain other properties. Thus, for example, the antimatter equivalent of the proton is the negatively charged antiproton, which is made of three antiquarks. It is a rule of nature that for every particle of matter that comes into existence, an antiparticle must also be created at the same time. It is fortunate for us that antimatter is not found in the everyday world, because when regular matter and antimatter come into contact, they annihilate each other in a burst of pure energy.