Quark–gluon plasma (QGP) is an unusual state of matter that appears under tremendous pressure and heat. At temperatures exceeding 100,000 times those at the Sun's center, particles such as protons and neutrons can no longer maintain their normal structure. Instead, they break apart into quarks and the gluons that ordinarily bind them together.

Physicists believe that this was the state of matter throughout the universe during the first millionths of a second after the Big Bang. Nearly 14 billion years later, researchers can briefly recreate these extraordinary conditions by smashing atomic nuclei together at extremely high energies inside the LHC.