During the first billion years, the Universe underwent its most dramatic transformation, evolving from a neutral, chemically simple state to an ionized, metal-enriched, and morphologically complex structure. This period represents a pivotal chapter in cosmic history, yet much about it remains poorly understood.

Key questions remain: - How long did reionization last? - What were the properties of the first stars? - Could black hole seeds at high redshift lead to the formation of supermassive black holes? - How rapid was chemical enrichment and how did it occur in early galaxies? - What is the nature of stellar populations of galaxies during this epoch?

Despite the uncertainties, significant progress has been made in the past decade toward understanding the formation and evolution of the first stars, galaxies, and black holes. Notable advancements include the new window opened by gravitational waves, strides in the study of the cosmological 21-cm line, ongoing developments in stellar archaeology and the unprecedented insights into the earliest galaxies provided by JWST. As observational capabilities grow, the need for robust simulations becomes increasingly critical. Simulations not only aid in interpreting current data but also offer predictions for the next generation of telescopes. This session aims to unite theorists to share the latest advancements and challenges of modeling all aspects of the first billion years of the evolution of the Universe. Thereby allowing us to bring together researchers from various subfields to engage in in-depth discussions and to develop connections across multiple synergistic areas such as star formation, stellar evolution, stellar clusters, binary interactions, chemistry, radiation, and cosmology.

Programme