In the last 20 years the spin structure of the nucleon spawned a very productive experimental and theoretical activity with exciting results and new challenges. The investigation of the nucleon spin structure has included a variety of aspects, such as testing QCD the theory of
strong interactions in its perturbative regime via spin sum rules (like the Bjorken sum rule) and understanding how the spin of the nucleon is build from the intrinsic degrees of freedom of the theory, namely quarks, gluons and their interactions. Results from a new generation of experiments performed at Jefferson Lab seeking to
address key issues in probing the theory in its non-perturbative regime, thus at low momentum transfers, will be presented. These results offer some insight in undesrtanding the transition region where the degrees of freedom are effective, like mesons and constituent quarks. Future planned experiments attempting to unravel
the effects of quark gluon correlations will be presented. Finally the extension of this spin physics program using 12 GeV upgrade of Jefferson Lab will be briefly discussed.

Host: Larry Zamick