I’m professor of physics and director of the Institute for Subatomic Physics at Utrecht University. Together with my colleagues and students in the institute I perform research in the ALICE experiment at the Large Hadron Collider (LHC) at CERN in Geneva. We study collisions of nuclei at very high energy, where we create matter of extreme density and temperature. From the properties of this matter we learn more about the strong interaction, one of the four fundamental forces in nature. The studies can also tell us more about the properties of the very early universe.