The Electroweak phase transition, heavy-ion collisions, the evolution of quantum fields in the early Universe; all require us to understand dynamical fields at finite temperature. So in this talk I will discuss how the Electroweak phase transition forces us to improve our understanding of non-equilibrium physics—as a whole. In particular, I will discuss how dissipation arises in various settings, and how it enters the evolution of gauge and scalar fields. This will also connect to analytical and numerical calculations of bubble-nucleation rates, and the inevitable effect on gravitational-wave predictions.