The goal of elementary particle physics is to understand the fundamental building blocks of matter. Since the beginning of the 20th century the picture of what is to be considered "elementary" had to be revised several times. Particles, which were once believed to be elementary, were found to be composed of even smaller particles. Moreover, the number of experimentally known particles grew quickly during the years. People therefore started to ask, is it possible to understand the large amount of experimental phenomena by a few basic ideas? Is there a theory which explains physics at this very small scales?

Nowadays we know that particles like the proton or the neutron are composed of quarks. Quarks themselves are currently believed to be elementary. The main interactions between the quarks are the strong interactions. Even at the beginning of the 21st century, understanding strong interactions remains one of the grand challenges of physics.

About 30 years ago, a theory emerged, which describes the properties of strong interactions, called Quantum Chromodynamics, or short QCD. Although QCD is an elegant theory based on a few fundamental ideas, it is very difficult to make quantitative predictions from first principles. Lattice formulations of QCD (lattice QCD) opened the way to study this theory using numerical methods.