Astronomy Colloquium

The era of the first galaxies and reionization is one of the final frontiers of observational cosmology. At the moment, a wide range of observations provide tantalizing - but often confusing - clues. I will summarize our current knowledge about this epoch and its low-redshift analog, when helium is fully ionized. I will then describe how future observations can settle some of the important open questions that remain. When did reionization occur? What sources were responsible? How did the intergalactic medium affect the process? And what did it do to future generations of sources?