Massive stars, due to their short lifetime and high energy output, drive the evolution of galaxies across cosmic time. Hence, they substantially contribute to shaping the present-day Universe. The Collaborative Research Centre (CRC) 1601 – called Sonderforschungsbereich (SFB) 1601 in German – aims to unravel the “habitats of massive stars across cosmic time”. "Habitats” are the gaseous environments within which massive stars are born and which they interact with via their feedback. CRC 1601 aims to connect the physical processes that govern the habitats of massive stars across the full range of environments hosting massive stars – from sub-parsec to mega-parsec scales and from the Milky Way to the high-redshift Universe, where massive stars leave their cosmological fingerprint by driving cosmic reionisation. The CRC 1601 joins forces to closely collaborate on the study of

• high-mass star formation at high resolution (project area A),
• massive star formation and signatures of high-mass star feedback on galactic scales (project area B), and
• the imprints of high-mass star formation on high-redshift galaxies and cosmic reionisation (project area C).