Metal and semiconductor nanocrystals show many unusual properties and functionalities, and can serve as model system to explore fundamental quantum and classical coupling interactions as well as building blocks of many practical applications. In this talk, I will show how to take the advantages of bottom-up chemical synthetic strategy to manipulate and fabricate artificial nanostructures that might not even exist in nature with meticulous control including defects, compositions and morphologies. Firstly, I will apply silver metal nanoparticles as an example and present a novel chemical synthetic technique to achieve unprecedented crystallinity control at the nanoscale. This engineering of nanocrystallinity enables manipulation of intrinsic chemical functionalities, physical properties as well as nano-device performance. Secondly, I will demonstrate a new general nonepitaxial growth strategy that achieves precise control of the hybrid core-shell nanostructures, whereby the monocrystalline shells are not dependent on the structure of the core nanoparticles. Importantly, these artificial integrated nanostructures with resonantly tailored interactions should serve as guiding principles for designing diverse nanosystems with improved optical, electric and magnetic properties for biological and energetic applications.