Our group studies chemical reactions of ultracold Rb atoms in a state-to-state resolved fashion, where we prepare reactants in well defined quantum states and measure the quantum states of the molecular products. In particular, we focus on three-body recombination where three atoms collide, forming a diatomic molecule. The third atom carries away part of the binding energy. We are currently investigating methods to gain control over this chemical reaction. By making use of either a magnetically tunable Feshbach resonance or an avoided crossing of molecular levels we can effectively construct different kinds of beam splitters for the reaction pathways. The idea is to resonantly admix at specific points of the reaction coordinate additional quantum states to the original collision complex. This opens up an additional pathway that the reaction can take. By tuning the magnetic field in our experiments, we can control these beam splitters and can redirect a sizeable fraction of the reaction flux between different product channels. These beam splitters are fully coherent and, in the future, it should be possible to use them also in interferometric schemes for controlling the reaction.