Whether catalyzing the formation of exotic mesons (e.g.meson photoproduction, N+gamma->N+pi) or probing the limitations of the the Standard Model (e.g. weak decays, B->K+pi+leptons), hadronic transitions lie at the core of present-day nuclear and particle physics research. Having a direct and reliable determination of these quantities from the Standard Model is both necessary and remarkably challenging due to the nonperturbative nature of the strong interaction. Said nonperturbative effects can now be adressed using lattice QCD. In this talk, I report on new techniques to study such reactions involving two or more hadrons in the initial and/or final state(s) via lattice QCD.