Bose–Einstein condensate (BEC) is a matter of a dilute gas of bosons which are cooled to a temperature very close to absolute zero (that is, very near 0 K or −273.15 °C). Under such conditions, a large fraction of bosons occupy the lowest possible quantum state at which point the macroscopic quantum phenomenon is most probable. It is formed by cooling a gas of extremely low density, that is about one-hundred-thousandth the density of normal air, to ultra-low temperatures.