The re-ionization history of cosmic hydrogen, left over from the big bang, provides crucial fossil evidence for when the first stars and black holes formed in the infant universe. Current observations provide a mixed message. The truth will likely be revealed over the next decade through observations of the Lyman-alpha spectra of galaxies, quasars and gamma-ray bursts, and most importantly the detection of the 21 cm transition from diffuse hydrogen at redshifts above 6.