  Exclusive, non-leptonic, two-body decays of B mesons simplify greatly in the
heavy quark limit. In this talk I discuss the factorized structure that holds
in this limit and some of its consequences: (a) naive factorization is
recovered in a certain limit; (b) `non-factorizable' effects are hard and can
be calculated; (c) strong interaction phases vanish in the heavy quark limit
(and can be calculated as well). As an illustration, I compute the penguin
contribution to the decay $B_d\to\pi^+\pi^-$ and its effect on the
determination of $\sin 2\alpha$.
