Quarks are the fundamental particles that make up most of ordinary matter. They are bound together by the strong nuclear force, mediated by the exchange of gluons as described by Quantum Chromodynamics (QCD). Quarks and gluons are not detected directly in experiments because of confinement; instead we see complicated bound states. By using simulations we are able to relate the bound state properties to those of the underlying quarks. The calculation is performed by constructing a discrete four dimensional space-time grid (the lattice) and then solving the QCD equations of motion on state-of-the-art high performance computers.