The article discusses the assembly of binary nanoparticle superlattices (BNSLs) using a variety of semiconductor, metallic, and magnetic nanoparticles. The authors demonstrate the formation of over 15 different BNSL structures, many of which have not been reported before. They show that the electrical charges on sterically stabilized nanoparticles play a crucial role in determining the BNSL stoichiometry, with additional contributions from entropic, van der Waals, steric, and dipolar forces stabilizing the structures. The study highlights the structural diversity of BNSLs, which defies traditional expectations and showcases the potential of modular self-assembly at the nanoscale. The formation of BNSLs with packing densities significantly lower than those of single-phase face-centered cubic (f.c.c.) close packing suggests that entropy is not the primary driving force for nanoparticle ordering. Instead, the Coulomb potential between oppositely charged nanoparticles stabilizes the BNSLs while destabilizing single-component superlattices. The authors also explore the effects of surfactant molecules on nanoparticle charges and their impact on BNSL formation. Overall, the work provides insights into the complex interplay of various forces in the assembly of BNSLs and opens new avenues for the design of metamaterials with programmable properties.The article discusses the assembly of binary nanoparticle superlattices (BNSLs) using a variety of semiconductor, metallic, and magnetic nanoparticles. The authors demonstrate the formation of over 15 different BNSL structures, many of which have not been reported before. They show that the electrical charges on sterically stabilized nanoparticles play a crucial role in determining the BNSL stoichiometry, with additional contributions from entropic, van der Waals, steric, and dipolar forces stabilizing the structures. The study highlights the structural diversity of BNSLs, which defies traditional expectations and showcases the potential of modular self-assembly at the nanoscale. The formation of BNSLs with packing densities significantly lower than those of single-phase face-centered cubic (f.c.c.) close packing suggests that entropy is not the primary driving force for nanoparticle ordering. Instead, the Coulomb potential between oppositely charged nanoparticles stabilizes the BNSLs while destabilizing single-component superlattices. The authors also explore the effects of surfactant molecules on nanoparticle charges and their impact on BNSL formation. Overall, the work provides insights into the complex interplay of various forces in the assembly of BNSLs and opens new avenues for the design of metamaterials with programmable properties.