Quantum mechanics represents the central revolution of modern natural science and its significance extends far beyond physics: neither chemistry nor biology on a molecular scale would be comprehensible without it. Modern information technology, from laptops to mobile phones and flat screens to supercomputers, would be unthinkable without quantum mechanical effects. It describes the world on the atomic and subatomic scale and is therefore the starting point of our modern worldview. At the same time, it poses a challenge: deeply rooted intuitive notions in humans about how the world functions, which were still compatible with the principles of classical physics, must be abandoned. Its acceptance is thus primarily based on the enormous empirical success it has achieved despite its relatively simple fundamental structure.