Soft materials such as nanoparticles and polymers show properties that are highly dependent on the nanoscale morphology as well as compositions. Thus, the ability to control their nanoscale morphology is important for both fundamental understanding and technological applications of nanomaterials. My thesis work concerned two distinct nanomaterials possessing strong structure-dependent optical properties: 1) silica-based multicomponent nanoparticles and 2) amphiphilic conjugated block copolymers. The multicomponent colloidal nanoparticles were composed of a fluorescent core and a metal shell separated by a silica spacer, where the florescence intensity from the core was controlled by adjusting the spacer thickness by layer-by-layer synthesis. The supramolecular assemblies of amphiphilic conjugated block copolymers exhibited highly tunable photoluminescence properties depending on their self-assembly structures. These studies demonstrated that the specific structures can be designed and synthesized to improve the material properties and that the optical properties can be controlled by the self-assembled structures in a predetermined way.