The question as to the origin of the hot thermal phase of the early universe represents a long-standing problem of particle cosmology. In this talk, we wish to make the case for the B-L phase transition, i.e. the cosmological realization of the spontaneous breaking of B-L at the end of hybrid inflation, as one particularly attractive and viable solution to this problem. As we are able to demonstrate, the B-L phase transition eventually transfers the initial vacuum energy driving inflation to an abundance of heavy (s)neutrinos. These (s)neutrinos decay into radiation, thereby reheating the universe, generating the baryon asymmetry of the universe and setting the stage for the thermal production of gravitinos. If gravitinos are light and stable, they themselves account for the relic density of dark matter; if they are very heavy and decay into neutralinos, dark matter can be explained in terms of nonthermal WIMPs. In either case we arrive at the conclusion that the B-L phase transition is able to successfully generate some of the most important initial conditions of the hot early universe in one go. On top of that, we find that these initial conditions are actually determined by the values of the parameters in the underlying Lagrangian, which renders the proposed scenario in principle testable in future experiments and observations.