We are at the beginning of a new generation of massive surveys of the sky, that will observe as many as 10 billion galaxies, including galaxies from the earliest epochs of their formation. We will use these surveys to answer some of the most profound questions about what the universe is made of, how it began, and how it evolves. At the heart of these questions is the link between the galaxies we observe, and the underlying matter that controls their evolution. I will describe this new generation of cosmological surveys, how we use numerical simulations and modeling to understand this link between galaxies and matter, and how we can use these two tools together to probe the physics of the dark cosmos as well as the physics of galaxy formation.
