The formation of the first stars and quasars marks the transition of the universe from its smooth initial state to its clumpy current state. In popular cosmological models, the first sources of light began to form at a redshift z=30 and reionized most of the hydrogen in the universe by z=7. I will describe the predicted properties of these sources and their effect on the surrounding intergalactic medium. Current observations are just starting to probe the hydrogen reionization epoch and to test these theoretical predictions.