  In the first part of the talk, we briefly review the problem of parton-energy
loss and thermalization at the Relativistic Heavy-Ion Collider and discuss how
heavy quarks (charm and bottom) can help to resolve the existing experimental
and theoretical puzzles. The second part of the talk is devoted to the
properties of heavy quarkonia in the (strongly interacting) Quark-Gluon Plasma
(sQGP) and their consequences for observables in heavy-ion collisions.
