In this article, we review the representative work that has been done by Hong-Jun Gao's group in the past two decades in Institute of Physics, Chinese Academy of Sciences. The work focuses on the construction, properties and applications of low-dimensional atomic/molecular crystals, covering the following 3 aspects.1) Construction and growth mechanisms of low-dimensional quantum structures. Firstly, we demonstrate the fabrication and growth mechanism of a seahorse shaped fractal pattern in C_(60)-TCNQ multi...