Antimatter
In particle physics, antimatter is the extension of the concept of the antiparticle to matter, where antimatter is composed of antiparticles in the same way that normal matter is composed of particles. For example, an anti-electron (a positron, an electron with a positive charge) and an anti-proton (a proton with a negative charge) could form an anti-hydrogen atom in the same way that an electron and a proton form a normal matter hydrogen atom. Furthermore, mixing matter and antimatter would lead to the annihilation of both in the same way that mixing antiparticles and particles does, thus giving rise to high-energy photons (gamma rays) or other particle–antiparticle pairs.
Antiparticles are also produced in any environment with a sufficiently high temperature (mean particle energy greater than the pair production threshold). During the period of baryogenesis, when the universe was extremely hot and dense, matter and antimatter were continually produced and annihilated. The presence of remaining matter, and absence of detectable remaining antimatter, also called baryon asymmetry, is attributed to violation of the CP-symmetry relating matter and antimatter.
Positrons are also produced via the radioactive beta+ decay, but this mechanism can be considered as "natural" as well as "artificial".
Antimatter cannot be stored in a container made of ordinary matter because antimatter reacts with any matter it touches, annihilating itself and the container. Antimatter that is composed of charged particles can be contained by a combination of an electric field and a magnetic field in a device. This device cannot, however, contain antimatter that consists of uncharged particles, for which atomic traps are used. In particular, such a trap may use the dipole moment (electrical or magnetic) of the trapped particles; at high vacuum, the matter or antimatter particles can be trapped (suspended) and cooled with slightly off-resonant laser radiation. Small particles can be also suspended by just intensive optical beam.