I am a theoretical nuclear astrophysicist working in the field of core-collapse supernovae. Such events determine the end of a massive star's life. What fascinates me about this subject of research is the numerical modeling. It requires not only the inclusion of nature's four fundamental forces, i.e. gravity, electromagnetism, strong, and weak interactions, but also the transport of neutrinos that are being produced from various weak processes and diffuse out of the initially imploding and later exploding stellar core. They are subject of terrestrial neutrino detection and can be used to probe (current limits of) the standard model of particle physics. I consider core-collapse supernova simulations as laboratories to study the impact of currently uncertain physics, e.g. to probe the state of matter at its extreme which cannot be obtained in current nuclear-physics experiments (temperatures on the order of 10¹¹ K and densities in excess of normal nuclear matter density). These are conditions which are reached in the intermediate-stage supernova remnants, (proto)neutron stars, some of the most extreme objects in the Universe. In case of a supernova explosion, they will develop towards cold neutron stars or collapse to a black hole in the absence of an explosion.