Quark-gluon plasma is a state of matter that exists at extremely high temperatures and densities, where quarks and gluons, the fundamental building blocks of protons and neutrons, are no longer confined within particles. This state is believed to have existed just moments after the Big Bang, when the universe was hot and dense enough for these particles to move freely. Scientists study quark-gluon plasma to understand the early universe and the fundamental forces of nature. Experiments at facilities like the Large Hadron Collider recreate conditions similar to those of the early universe, allowing researchers to observe and analyze this unique state of matter.