Exploring the proton's spin

To understand the inner structure of the proton is a fundamental quest of nuclear research. The spin of the proton is of key importance in this context: How is the spin ℏ /2 built up from the spins and orbital angular momenta of the quarks and gluons inside the proton?

This seemingly simple question has preoccupied the community for decades, leading to discoveries and presenting puzzles.

The talk gives a synopsis of the historical development of the field, describes the current results and status, and gives an outlook on future opportunities.