Mitochondria are dynamic organelles that continuously undergo opposing processes of fission and fusion. Dynamin related protein 1, Drp1, is a largely cytosolic GTPase and is the master regulator of mitochondrial fission. However for its mitochondrial recruitment, Drp1 requires receptor/adaptor proteins on the mitochondrial outer membrane surface. So far, Fis1, Mff, MiD49 and MiD51 have been identified in mammalian cells to play a role in Drp1 recruitment to mitochondria, yet the molecular mechanisms underlying the interactions are not clearly understood. Drp1 and the cytosolic domains of Fis1, Mff and MiD49 and MiD51 proteins have been purified for in vitro analysis. The purified proteins are also being used in numerous in vitro assays to characterize interactions and determine the effect on the GTPase activity and polymerization of Drp1. Antibodies are being generated for protein levels in cultured cell extracts, co-immunoprecipitation assays and tissue expression studies. These studies will help to further elucidate the molecular mechanisms involved in the process of fission which is linked with mitochondrial function and diseases.