"The appearance of the first stars marked a primary transition in cosmic history. Their light ended the so-called “dark ages”, and they played a key role in the metal enrichment and the reionization of the Universe, thereby shaping the galaxies we see today. Understanding high-redshift star formation is central to many areas of modern astrophysics. However, studying stellar birth in the early Universe is a relatively young field of science, and so still little is known about the origin and observablecharacteristics of the first stellar populations. Shedding light on the physical processes that governthe formation of stars in the early Universe requires a concerted, multi-facetted approach thatcombines a range of complementary expertise and innovative techniques. Using novel, high-resolution computer simulations we will (1) identify the physical phenomena that led to the formation of the first and second generations of stars in a systematic and quantitative way, (2) determine their mass distribution, which is the key parameter setting their lifetimes, luminosities, and chemical yields, (3) study the influence of the first stars on their surrounding environment, and (4) by doing so learn more about the subsequent cosmic evolution. We will set up a comprehensive theoretical and computational framework that enables us for the first time to make clear predictions and to compare our results with observational data from the high-redshift Universe as well as from the oldest stellar population in the Milky Way."