ALICE is optimized to study heavy-ion (Pb-Pb nuclei) collisions at a centre of mass energy of 2.76 TeV per nucleon pair. The resulting temperature and energy density are expected to be high enough to produce quark–gluon plasma, a state of matter wherein quarks and gluons are freed. Similar conditions are believed to have existed a fraction of the second after the Big Bang before quarks and gluons bound together to form hadrons and heavier particles. ALICE is focusing on the physics of strongly interacting matter at extreme energy densities. The existence of the quark–gluon plasma and its properties are key issues in quantum chromodynamics for understanding color confinement and chiral symmetry restoration. Recreating this primordial form of matter and understanding how it evolves is expected to shed light on questions about how matter is organized, the mechanism that confines quarks and gluons and the nature of strong interactions and how they result in generating the bulk of the mass of ordinary matter.