  While the form factors and parton distributions provide separately the shape
of the proton in coordinate and momentum spaces, a more powerful imaging of the
proton structure can be obtained through phase-space distributions. Here we
introduce the Wigner-type quark and gluon distributions which depict a full-3D
proton at every fixed light-cone momentum, like what seen through
momentum("color")-filters. After appropriate phase-space reductions, the Wigner
distributions are related to the generalized parton distributions (GPD's) and
transverse-momentum dependent parton distributions which are measurable in
high-energy experiments. The new interpretation of GPD's provides a classical
way to visualize the orbital motion of the quarks which is known to be the key
to the spin and magnetic moment of the proton.
