Matter consists of quarks. The building blocks of atomic nuclei, protons and neutrons, are composed of these fundamental particles – held together by gluons. These act as glue (English glue = Klebstoff) and hold the quarks together. However, the theory of the strong nuclear force predicts something else: gluons should also be able to bind to each other – forming so-called “gluon balls”, particles without any quark content, essentially matter made of pure cohesion.