The end of a massive star is marked by a supernova, the extremely energetic explosion that follows the gravitational collapse of a star which burned all of his nuclear fuel. Under some conditions the collapse stalls and the star's now highly compressed core forms a compact neutron star. Due to their small radius of about 12 km and high masses of up to two solar masses neutron stars consist of the most dense matter we can observe in our universe. Despite an increasing amount of data the internal composition of neutron stars is not yet understood. Originally these objects have been assumed to consist of neutron rich hadronic matter (hence neutron stars). With the development of Quantum Chromo Dynamics it had been realized that the gravitational pressure inside a neutron star can be strong enough to transform hadronic matter into a quark-gluon plasma. The same state of matter is searched for in present and future heavy ion collision experiments as RHIC, FAIR and NICA. In my presentation I will outline how these three directions of contemporary research - investigating the physics of neutron stars, heavy-ion collisions and the theory of QCD - complement each other and broaden our understanding of the strong interaction.