A laser beam is made of coherent light which gives it many important uses. The term laser itself is an acronym for light amplification by stimulated emission of radiation. Today, there are many varieties of lasers, but the Ruby laser was the first. At the core of the Ruby laser is a bar of synthetic Ruby. At each end of the bar is a mirror, one of which is transparent enough to allow light to. Thus, coiled around the bar is a flash lamp. Ordinary light is incoherent with many wavelengths moving in different directions. A laser generates coherent light, which means its waves move in unison at the same wavelength. A light of singular intensity and power. How coherent light is produced begins at the atomic level. The smallest unit of light is a photon, which can be emitted from an atom when an electron reduces its energy level. When light is flashed into a Ruby rod, it stimulates the ruby's atoms, sending its electrons to a higher energy level. As the light rays bounce between the mirrors at each end, more and more atoms are stimulated. When the electrons of the Ruby atoms return to their natural energy state almost at the same time, they release a host of photons of a single wavelength that emerges through the partially transparent mirror in a beam of coherent light. Lasers are now used throughout society, from CD players to grocery counters, where the bar code on the package is scanned by a laser which relays information both to the cash register and the store's inventory system.