  We discuss the recent interpretation of quark-distribution functions in the
plane transverse to the light-cone direction. Such a mapping is model
independent and allows one to build up multidimensional pictures of the hadron
and to develop a semi-classical interpretation of the quark dynamics. We
comment briefly the results obtained from the form factors of the nucleon. We
show that a generalization to a target with arbitrary spin leads to a set of
preferred values for the electromagnetic coupling characterizing structureless
particles. Finally, we present the Wigner distribution for an unpolarized quark
in an unpolarized proton and we propose an interpretation of the observed
distortion as due to the orbital angular momentum of the quark.
