Colloidal semiconductor heterostructures are efficient luminescent materials for light emitting applications based on their unique optical properties such as size-dependent band gap energy, narrow emission linewidth and high photoluminescence quantum yield (PL QY) and photochemical stability. Particularly, to boost the optical performance and efficiency of the light-emitting devices, high PL QY of colloidal semiconductor heterostructures is necessary. The common way to attain high quantum yield is passivating weak organic ligand and dangling bond on the surface of nanocrystal cores with wide bandgap semiconducting inorganic shell and called it as core/shell heterostructure. In this study, I discuss about the understanding and engineering of the relationship between optical properties and structure of nanocrystals via precise control of composition, electronic and morphological structure and surface and interface of nanocrystals. With this, I also demonstrate new heterostructures based on the coherently strained structures. For the perspective approach to commercialization of colloidal semiconductor heterostructure, I propose colloidal core/shell heterostructure with III-V/II-VI semiconductor heterovalent interface for highly luminescent cd-free nanocrystals.