I study the evolution, fate and impact of stars. Stars play a key role in the Universe through the light they shine, their kinetic feedback via winds and supernovae and the chemical elements they produce. They are complex objects involving many physical processes: turbulence (convection), interaction of rotation and magnetic fields and nuclear reactions. Ideally, we would like to model the structure and evolution of stars using three-dimensional (3D) magneto-hydrodynamics simulations. The large spread in length scales and the lifetime of stars being many orders of magnitude longer than the convective timescale, however, implies that we need to model the global evolution of stars using one-dimensional (1D) stellar evolution models. During my PhD, I improved 1D models to study the impact of rotation on the late phases of the evolution of massive stars. I then went to the Universität Basel as a postdoctoral fellow to determine the comprehensive nucleosynthesis taking place in massive stars, in particular the so-called weak s process. Since joining Keele University in 2007, major highlights of my research have been the determination of the mass and fate of the most massive stars known to date, explaining unique abundances in the early Universe and the setting-up and leading of large projects (ERC starting grant for SHYNE project 2012-2017) and collaborations (NUGRID, BRIDGCE, ChETEC COST Action). The goal of my theoretical research is to link major nuclear physics experiments to large astronomical observing programmes, 3D hydrodynamics simulations to 1D stellar models and theoretical stellar astrophysics to the high performance computing industry.