The paper introduces a gauge-invariant decomposition of the nucleon spin into quark helicity, quark orbital, and gluon contributions. The total quark (and quark orbital) contribution is shown to be measurable through virtual Compton scattering in a special kinematic region where single quark scattering dominates. This process, known as deeply-virtual Compton scattering (DVCS), has significant potential to unravel the quark and gluon structure of the nucleon. The author demonstrates that the gauge-invariant decomposition allows meaningful calculations and measurements of the fraction of the nucleon spin carried by quarks and gluons. The leading-log evolution of the quark and gluon contributions to the nucleon spin is derived, showing that the ratio of their contributions asymptotically approaches 16:3n_f, where n_f is the number of active fermion flavors. The paper also discusses the practical aspects of measuring these contributions, including the use of DVCS and other processes like diffractive ρ or J/ψ production.The paper introduces a gauge-invariant decomposition of the nucleon spin into quark helicity, quark orbital, and gluon contributions. The total quark (and quark orbital) contribution is shown to be measurable through virtual Compton scattering in a special kinematic region where single quark scattering dominates. This process, known as deeply-virtual Compton scattering (DVCS), has significant potential to unravel the quark and gluon structure of the nucleon. The author demonstrates that the gauge-invariant decomposition allows meaningful calculations and measurements of the fraction of the nucleon spin carried by quarks and gluons. The leading-log evolution of the quark and gluon contributions to the nucleon spin is derived, showing that the ratio of their contributions asymptotically approaches 16:3n_f, where n_f is the number of active fermion flavors. The paper also discusses the practical aspects of measuring these contributions, including the use of DVCS and other processes like diffractive ρ or J/ψ production.