In this unit, we provide intuitional background for studying Jeremy England's recent paper, "Statistical physics of self-replication," at a level mostly appropriate for algebra-based high school physics courses. To understand the irreversibility of a macroscopic state change, it is important to compare the volumes of the portions of phase space corresponding to two macrostates within the volume of phase space that is kinetically accessible. In this video, we provide probabilistic language for describing the dynamic exploration of microstates of a universe.