The universe today is fascinatingly complex. Hundreds of billions of galaxies are each home to hundreds of billions of stars, planets, and other astronomical objects. But 14 billion years ago, the universe looked quite different: it contained a nearly uniform plasma, whose temperature varied from point to point by just one part in 100,000. There are many competing explanations for why the early universe looked this way, including a variety of “inflationary” models in which the universe is forced to grow tremendously in just a small fraction of a second. Ideally, these models work in two steps: First, turn the initial state of the universe into something completely homogeneous; and second, produce small fluctuations on top of that uniform background. It’s easy to check by hand that most of these models can accomplish the second step, but that’s because Einstein’s Equations are relatively simple when the universe is already homogeneous. To check whether a model can accomplish the first step, I use computer simulations to solve Einstein’s Equations numerically and track how the universe evolves, starting from an initially inhomogeneous state. If the model successfully causes the universe to smooth out, then it passes my test—but if the universe remains a wild mess, then we know the explanation is inomplete. So far, we’ve seen that some of the most popular models of inflation actually fail this test, motivating explorations of alternative models of inflation or even entirely different explanations for the observed state of the early universe.