A good method for homogeneous catalysts separation and reuse is offered by the use of biphasic liquid–liquid systems. Recycling can be achieved in the reactor when the organic phase is sampled out, while the aqueous phase containing the catalyst is retained into the vessel, enabling for continuous processing. The main issue that has to be solved in such set-up is the tolerability of the catalyst to water (its solubility, its activity, etc.) . A strategy to overcome this problem is the inclusion and confinement of the homogeneous catalysts into a host nano-architecture . Compartmentalization enables catalyst segregation and shielding, and ensures its facile removal from the reaction mixture after the reaction has taken place ; this facilitates reactions to be performed in water followed by liquid–liquid separation of products and catalyst . Moreover, shielding and segregation of catalysts in a nanoreactor facilitates one-pot tandem reactions that, in most cases, require two or more incompatible catalysts . Catalyst confinement leads to a high local concentration of the substrate at the active site, which results in higher reaction rates and better conversion . In this review we will highlight some typical nanoreactors that are used to accommodate homogeneous catalysts, holding promise in green organic synthesis. A division will be made between self-assembled nanoreactors, section 2, and covalent systems, section 3.