The first generation of stars likely formed at very high redshifts, z>20, at locations corresponding to rare peaks of the fluctuating primordial density field. In the absence of any feedback processes, these stars could form in abundance and they, and their accreting black hole (BH) remnants, could significantly reionize the intergalactic medium (IGM). However, the population of the first stars and BHs were likely self-regulating due to their global chemical, radiative, and thermodynamical impact on the IGM, and further star-formation and reionization was delayed as a result. The low electron scattering optical depth in the three-year WMAP data already offers empirical support that the ionizing photon production in the earliest objects was suppressed. I will discuss the physical processes that are expected to have determined the size and evolution of the first stellar clusters and black holes, and which could have caused this suppression. I will also discuss the prospect of learning about these processes in future observations.