Growth and understanding of novel properties of nanostructures have become one of the most exciting research areas. This is driven by their great potential technological applications and scientific significance to bridge our understanding between atom/molecule and condensed matter physics. The beneficial structural, electronic, optical, magnetic, and chemical properties of nanostructures can be applied in many fields. Using sophisticated experimental techniques (MBE, STM/STS, ARPES, transport), we have explored a diverse set of research topics, including atomic-level control of nanostructure growth, quantum size effects in thin films, interfacial superconductivity, topological insulators, and so on. In this paper, I mainly focus on the quantum size effects in thin films and enhanced high-temperature superconductivity at the interface.