Flavor-changing neutral current decays such as b->sll are highly suppressed in the Standard Model (SM) and therefore provide sensitive tests for new physics. The long-standing tension between SM predictions and experimental measurements in both branching ratios and angular observables in b->sll decays can be attributed to a modification of the Wilson coefficient C9 of the semileptonic effective operator O9 by approximately 20–25 % relative to its SM value. This deviation might originate from a short-distance b->sll contribution, signaling new physics, or from unaccounted-for long-distance contributions within the SM, arising from the non-local matrix elements of the four-quark operators. We discuss our current theoretical understanding of these non-local matrix elements, focusing in particular on rescattering contributions induced by intermediate D^(*) D^(*)_s states.