Time crystals (TCs) are many-body systems that display spontaneous breaking of time translation symmetry. We demonstrate a TC by using driven-dissipative condensates of microcavity exciton-polaritons, spontaneously formed from an incoherent particle … Time crystals (TCs) are many-body systems that display spontaneous breaking of time translation symmetry. We demonstrate a TC by using driven-dissipative condensates of microcavity exciton-polaritons, spontaneously formed from an incoherent particle … Science