Quark–gluon plasma is a very high-temperature phase in which quarks become free and able to move independently, rather than being perpetually bound into particles, in a sea of gluons, subatomic particles that transmit the strong force that binds quarks together. This is analogous to the liberation of electrons from atoms in a plasma. This state is briefly attainable in extremely high-energy heavy ion collisions in particle accelerators, and allows scientists to observe the properties of individual quarks. Theories predicting the existence of quark–gluon plasma were developed in the late 1970s and early 1980s, and it was detected for the first time in the laboratory at CERN in the year 2000. Unlike plasma, which flows like a gas, interactions within QGP are strong and it flows like a liquid.