Sela proved that the first order theory of torsion free hyperbolic groups, and therefore that of free groups, is stable. This result implies that there is a notion of independence in the free group. Perin and Sklinos succeeded to characterize forking independence in the free group in a purely group theoretic way by introducing a special kind of JSJ decomposition of a free group relative to a set of parameters. In my talk I will present this result as well as some special cases where it is easier to understand forking independence.