Where does the nucleon spin come from?

The theory of quantum chromodynamics designates quarks as the basic building blocks of matter and gluons as the carriers of strong force between quarks. It was postulated that these quarks and gluons build up particles such as protons and neutrons, collectively known as nucleons. Although the exact dynamics that led to the formation of protons and neutrons are unknown, the spin structure of the nucleon is thought to provide some clues. The recent findings by the European Muon Collaboration are presented in this article that have gained better insight into the nucleon structure.