  This contribution presents the latest results on heavy quarkonia (j/psi and
upsilon) production in d+A and A+A collisions at RHIC at a center of mass
energy per nucleon-nucleon collision sqrt(s_NN) = 200 GeV, measured by the
PHENIX experiment, as well as their implications in terms of understanding cold
nuclear matter effects and the possible formation of a quark gluon plasma in
central $\auau$ collisions.}
