I am a relativistic astrophysicist: i.e. a physicists that uses Einstein’s theory of general relativity to describe and explain astronomical observations of black holes and neutron stars. To do this I combine analytical perturbative tools with numerical nonlinear simulations in which I solve the Einstein equations together with those of relativistic hydrodynamics or magnetohydrodynamics. I do this in the endless process of comparing theoretical results and predictions with astronomical observations. Previously an Associate Professor and Director of the Computing Centre at SISSA (Italy), I now lead a group of scientists and students at the Albert Einstein Institute working on the modelling of sources of gravitational waves.