Superparamagnetic iron oxide nanoparticles are of great interest in the field of biomedicine at present due to their highly tuneable magnetic properties, which can be modulated by the application of an external magnetic field. Controlled assembly of these nanoparticles to form functional clusters allows for the improved and nuclear magnetic response, while retaining advantageous superparamagnetic character. In the first half of this thesis a novel approach for the controlled assembly of nanoparticles by a polymer mediated approach to form superparamagnetic clusters is introduced. Process optimization and the effects of assembly on the magnetic and magnetic resonance response are investigated. In the second half, nanoparticle morphology is addressed; in particular the production of cubic nanoparticles and the assembly of these into functional clusters with higher inherent magnetocrystalline anisotropy is described.