Antihydrogen consists of a positron in orbit around an antiproton and was first produced at CERN towards the end of 1995.
According to the CPT theorem, antihydrogen should have the same atomic spectrum as hydrogen. The challenge now is to trap antihydrogen atoms at cryogenic temperatures for long enough to allow precision tests of the CPT theorem.
Antimatter and matter annihilate instantly when they encounter one another. It takes more energy to produce antimatter than is released when it annihilates, so, contrary to many science-fiction novels, antimatter will never be a viable energy source.
One of the most staggering achievements in quantum physics was Paul Dirac's prediction of the anti-electron in 1930. By tirelessly modifying Schrödinger's description of the electron until it was consistent with special relativity, Dirac derived a beautiful equation that had additional "negative energy" solutions. He proposed that these solutions corresponded to a particle that has the same mass as the electron but the opposite electrical charge. Three years later the world's first antiparticle - called the positron - was discovered by Carl Anderson at the California Institute of Technology.