  Transport equations have been applied successfully to describe the quarkonium
evolution inside the quark-gluon plasma, which include both plasma screening
effects and recombination. We demonstrate how the quarkonium transport equation
is derived from QCD by using the open quantum system framework and effective
field theory. Weak coupling and Markovian approximations used in the derivation
are justified from a separation of scales. By solving the equations
numerically, we study the Upsilon production in heavy ion collisions.
