Massive stars are rare and short-lived. Nevertheless, through their extreme brightness, strong outflows and powerful explosions, they heat and stir their surroundings, drive outflows on galactic scales, and are responsible for the main production heavy elements in the Universe. For this reason, stellar models of massive stars are an essential ingredient for a wide variety of astrophysical problems.
I will discuss advances in the massive star community triggered by new large spectroscopic surveys, such as the Tarantula Survey, that allow us now to populate the Hertzsprung-Russel diagram with stars up to 300 solar masses. Furthermore, I will discuss new constraints on impact of stellar rotation and the importance of binarity.
The theoretical and observational developments in this field call for a critical reconsideration of our understanding of the role that massive stars play in the Universe as Cosmic Engines, i.e. through their chemical, mechanical and radiative feedback, as Cosmic Probes, i.e. as tracers of starformation nearby and at high redshift, and in the variety of Cosmic Transients they produce.