  Light-cone Fock-state wavefunctions encode the properties of a hadron in
terms of its fundamental quark and gluon degrees of freedom. A recent
experiment at Fermilab, E791, demonstrates that the color coherence and shape
of light-cone wavefunctions in longitudinal momentum fraction can be directly
measured by the high energy diffractive jet dissociation of hadrons on nuclei.
Given the proton's light-cone wavefunctions, one can compute not only the quark
and gluon distributions measured in deep inelastic lepton-proton scattering,
but also the multi-parton correlations which control the distribution of
particles in the proton fragmentation region and dynamical higher twist
effects. First-principle predictions can be made for structure functions at
small and large light-cone momentum fraction $x$. Light-cone wavefunctions also
provide a systematic framework for evaluating exclusive hadronic matrix
elements, including timelike heavy hadron decay amplitudes and form factors. In
principle, light-cone wavefunctions can be computed in nonperturbative QCD by
diagonalizing the light-cone Hamiltonian using the DLCQ method, as in
dimensionally reduced collinear QCD.
