The first stars and galaxies had a profound impact on the universe, leading to reionization and the chemical enrichment of the intergalactic medium.  Here I present results from adaptive mesh refinement radiation hydrodynamics simulations that focus on the formation of the first galaxies with a self-consistent transition from massive metal-free stars to metal-enriched stars that populate the first galaxies. These results provide invaluable insight for interpreting the latest and future galaxy observations prior to reionization.