  We derive noncommutative multi-particle quantum mechanics from noncommutative
quantum field theory in the nonrelativistic limit. Paricles of opposite charges
are found to have opposite noncommutativity. As a result, there is no
noncommutative correction to the hydrogen atom spectrum at the tree level. We
also comment on the obstacles to take noncommutative phenomenology seriously,
and propose a way to construct noncommutative SU(5) grand unified theory.
