The Lost Tribes of Charmonium

To illustrate the campaign to extend our knowledge of the charmonium spectrum, I focus on a puzzling new state, X(3872)→π+π−J/ψ. Studying the influence of open-charm channels on charmonium properties leads us to propose a new charmonium spectroscopy: additional discrete charmonium levels that can be discovered as narrow resonances of charmed and anticharmed mesons. I call attention to open issues for theory and experiment.