The Standard Model of Elementary Particle Physics (SM) summarizes our knowledge about the fundamental constituents of matter and their electromagnetic, weak and strong nuclear interactions. In particular, Quantum Chromo-Dynamics (QCD) is the part of the SM describing the strong nuclear interaction, in terms of gluon exchange between quarks. In contrast to this theoretical description, experiments can only manipulate and detect bound states of quarks and gluons, such as protons or pions. This phenomenon, known as quark confinement, raises the question as to how one may even define quark masses or the coupling strength between quarks and gluons, which play the role of fundamental parameters in the Standard model. 

In this talk I will explain how asymptotic freedom of quarks allows for a satisfactory solution and I will then describe a high precision determination of the strong coupling constant, based on low energy experimental input and numerical simulations of lattice QCD. This result will help improve SM predictions for collider experiments and thus enhance their sensitivity to effects of yet unknown physics.