A quark–gluon plasma (QGP) or quark soup is a state of matter in quantum chromodynamics (QCD) which is hypothesized to exist at extremely high temperature, density, or both temperature and density. This state is thought to consist of asymptotically free quarks and gluons, which are several of the basic building blocks of matter. It is believed that up to a few milliseconds after the Big Bang, known as the Quark epoch, the Universe was in a quark–gluon plasma state. In June 2015, an international team of physicists produced quark-gluon plasma at the Large Hadron Collider  by colliding protons with lead nuclei at high energy inside the supercollider’s Compact Muon Solenoid detector. They also discovered that this new state of matter behaves like a fluid.