The Big Bang is the term which refers to the origin point of the universe, an instantaneous expansion of a microscopic singularity.
While attempting to flee from his fellow Q, Quinn transported the USS Voyager to a point in time shortly after the Big Bang. B'Elanna Torres remarked that Voyager was not capable of surviving the formation of the cosmos. Q retorted by stating she should consider it an honor to have her atoms become part of the entire universe. (VOY: "Death Wish")