  We report recent progress on understanding the thermalization of the
quark-gluon plasma during the early stage in a heavy ion collision. The
initially high overpopulation in the pre-equilibrium gluonic matter
(``glasma'') is shown to play a crucial role. The strongly interacting nature
(and thus fast evolution) naturally arises as an {\em emergent property} of
this pre-equilibrium matter where the intrinsic coupling is weak but the highly
occupied gluon states coherently amplify the scattering. A possible transient
Bose-Einstein Condensate is argued to form dynamically on a rather general
ground. We develop the kinetic approach for describing this highly
overpopulated system and find approximate scaling solutions as well as
numerically study the onset of condensation. Finally we discuss possible
phenomenological implications.

High Energy Physics - Phenomenology;Nuclear Experiment;Nuclear Theory