  I discuss issues related to charmonium production, in view of physics
possibilities at a 15 ... 30 GeV continuous beam electron facility. High energy
photo- and hadroproduction of heavy quarkonia presents several challenges to
QCD models concerning cross sections, polarization and nuclear target
dependence. Theoretical approaches based on color evaporation as well as on
color singlet and color octet mechanisms have met with both successes and
failures, indicating that charmonium production is a sensitive probe of color
dynamics. Experiments close to charm kinematic threshold will be sensitive also
to target substructure since only unusual, compact target configurations
contribute. In particular, subthreshold production on nuclei should identify
nuclear hot spots of high energy density. At low energies, charmonium will form
inside the target nucleus, allowing a determination of c cbar bound state
interactions in nuclear matter.
