Before the universe was illuminated by stars, most of its observable matter existed in a roughly even distribution of hydrogen and helium. As these materials collapsed under their own gravity, they would have heated up, initially preventing them from collapsing further to densities high enough for stars to form. As part of a new review, Prof. Dr. Ralf Klessen and Prof. Dr. Simon Glover at Heidelberg University investigate the chemical mechanisms which enabled this primordial gas to cool and fragment to form the universe’s first generation of stars.