We study the respective impact of stellar winds, ionizing radiation, and supernovae in modern simulations of the multi-phase interstellar medium in parts of galaxies within the SILCC project, which I will present in this talk. From these galactic scale simulations we find that ionizing radiation is the most important factor in regulating the star formation rate, while supernova over-pressure the gas substantially, thus driving a galactic outflow.
Yet massive star formation occurs on sub-parsec scales, within the densest and coldest parts of molecular clouds. To date it is not really clear how long newly born massive stars stay deeply embedded within their parental dense cores. We address this question by means of massive star formation simulations that cover a variety of environments. I will show the latest results of this ongoing study.