Introduction and motivations

Despite theoretical progress and rapid advances in the discovery of high-redshift galaxies, many questions about the first stars remain open: What was their IMF? How long did the epoch of metal-free stars last? Did they contribute much to reionization? Do their remnants include compact objects, and if so, where are they? The highly interdisciplinary “first stars” field is just beginning to confront observations in the form of reionization tests with the Gunn-Peterson effect and the Wilkinson Microwave Anisotropy Probe (WMAP), and chemical abundances from extremely metal-poor Galactic stars. These indicators have yielded some indirect constraints on the nature of the first stars. I believe that neither high-z galaxies nor the “second stars” will tell the whole story on their own.