Supernovae are amazing cosmic explosions where for a few weeks to months a single star can become as bright as a billion stars combined. Even though supernovae are key for a wide range of areas in astrophysics, from understanding nucleosynthesis to galactic evolution to measuring the accelerating expansion of our Universe, the actual progenitors of these explosions are frustratingly elusive to find. This is now changing with new observations that are allowing us to catch supernovae earlier than ever before, often days if not hours after the explosion first begins. I will discuss theoretical work showing how this early phase is key for learning about the progenitors of these explosions by measuring fundamental quantities such as the star’s mass, radius, and properties of the circumstellar material around the star in the moments before the supernova. These new results have confirmed many of our suspicions about exploding stars, and maybe not surprisingly, also have brought to our focus some new mysteries.