Nanoparticles can be viewed as a new type of "atom" with size dependent physical, optical and electronic properties that make them suitable for a wide variety of applications. There are many open questions in the field of nanoparticle synthesis and assembly. For example: How does the nanoparticle-nanoparticle potential govern nanoparticle formation or assembly? Can one design a nanoparticle from the ground up, according to theoretical predictions, which will self-assemble into a given nanoparticle superlattice structure? How does the assembly process vary with nanoparticle shape (e.g., spherical, rod, triangular, square, etc.) and the ligand coating which surrounds each nanoparticle? Can one make more robust nanoparticle superlattice structures, of macroscopic size (millimetre to centimetre), which can be moulded, milled and machined into desired shapes? Can one make nanoparticles that are stable at high temperature so that their assemblies can be melted, alloyed and cast? These questions cannot be answered in isolation. A successful attack on these difficult questions requires the coordinated and collaborative effects of nanoparticle theorists, synthesizers, and assemblers.