In this paper we report the conversion of an InP Magic Size Cluster (MSC) to a Cd3P2 MSC through a cation exchange mechanism, and attempt to shed light on the evolution of the physical and electronic structure of these clusters during the transformation. We demonstrate retention of the original InP MSC crystal lattice as Z-type ligand exchange initially occurs. Further cation exchange induces lattice relaxation and a significant structural rearrangement. These observations contrast with reports of cation exchange in InP quantum dots, indicating unique reactivity of the InP MSC. The paper can be found here.