The optical properties of disordered nanocrystal assemblies can be expanded and continuously tuned by incorporating hierarchical compositional heterogeneity, at the atomic level, through elemental doping of nanocrystals, and at the super-atomic level, through mixing of nanocrystals within assemblies. Random mixing of particles with similar physical features but distinct chemical compositions provides a straightforward method to achieve mixingtunable collective plasmon resonance in nanocrystal gels and superlattices (Figure ).