  We discuss the integrability of Jacobi manifolds by contact groupoids, and
then look at what the Jacobi point of view brings new into Poisson geometry. In
particular, using contact groupoids, we prove a Kostant-type theorem on the
prequantization of symplectic groupoids, which answers a question posed by
Weinstein and Xu \cite{prequan}. The methods used are those of
Crainic-Fernandes on $A$-paths and monodromy group(oid)s of algebroids. In
particular, most of the results we obtain are valid also in the non-integrable
case.
