2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/45216We review the spectroscopy and some properties of hadrons containing two charmed quarks, or more generally, two heavy quarks. This includes heavy baryons such as $(bcu)$, and possible exotic multiquark states.Talk given at the CHARM 2000 Workshop, Fermilab, June 1994 to appear in the Proceedings Latex, style file "charm2000" appendedHigh Energy Physics - Phenomenologytext