The visible universe is roughly 60 orders of magnitude larger than the Planck length, where classical spacetime gives way to quantum foam. This ratio is thus a rough lower bound on the overall expansion of space since the Big Bang. Of these 60 factors of ten, 30 would be accounted for by inflation — the hypothetical period of accelerated expansion in the early universe. The next 15 factors of ten take roughly a trillionth of a second, while the final 15 require the 13.8 billion years which elapse between that moment and the present day. It is only in this final era that typical temperatures and energies in the Universe are below the TeV scale, the presumed range of validity of the Standard Model of particle physics. This intermediate epoch — sometimes called the Primordial Dark Age — is often overlooked by cosmologists and while it lasts an eye-blink it accounts for a quarter of the total growth of the Universe, logarithmically speaking. I will discuss how this epoch can host complex nonlinear dynamics, influence key cosmological observables, and yield distinctive observational signatures as well as providing potential insights into ultra-high energy particle physics.