There are two main disciplines in catalysis research -- homogeneous and heterogeneous catalysis. This is due to the fact that the catalyst is either in the same phase (homogeneous catalysis) as the reaction being catalyzed or in a different phase (heterogeneous catalysis). Over the past decade, various approaches have been implemented to combine the advantages of homogeneous catalysis (efficiency, selectivity) with those of heterogeneous catalysis (stability, recovery) by the heterogenization of homogeneous catalysts or by carrying out homogeneous reactions under heterogeneous conditions.