The evidence for a hot, dense, early stage of the Universe is overwhelming. Setting up a Universe in this hot-dense stage is more of a challenge. While Cosmic Inflation as a paradigm has been successful at negotiating the issues of the Hot Big Bang, its conclusion is marked by a cold, empty state that needs to quickly and efficiently reheat. Violent processes, turbulent phase transitions and non-linear processes characterize this period and might help us shed light on the particle physics of the very young, very energetic early Universe. I will describe how we have been using large numerical simulations to calculate precision observables that will help to constrain the growing number of early universe scenarios.