  I introduce a gauge invariant decomposition of the nucleon spin into quark
helicity, quark orbital, and gluon contributions. The total quark (and hence
the quark orbital) contribution is shown to be measurable through virtual
Compton scattering in a special kinematic region where single quark scattering
dominates. This deeply-virtual Compton scattering (DVCS) has much potential to
unravel the quark and gluon structure of the nucleon.
