Ultra-small nanocrystals are nanoscale materials. Since the size of ultra-small nanocrystals is comparable to or even smaller than the Bohr exciton diameter of the materials, ultra-small nanocrystals exhibit significant enhanced physical properties, such as magnetic, optical and electronic properties. As the size of a nanocrystal becomes smaller quantum effects, increased astoichiometry, and defects can give rise to many interesting property transitions, including a metal to semiconductor transition, and a diamagnetic to ferromagnetic transition. Facile colloidal synthesis of ultra-small nanocrystals allows one to explore the interesting optical, magnetic, and electrical properties of these materials with extremely small sizes at the nanoscale. The research on the synthetic chemistry as well as the physical properties of these ultra-small nanocrystals helps to enhance the applicability of these nanocrystals in device applications. A necessary step towards the application of these nanocrystals is their uniform film assembly. The efficient film deposition technique, as presented in this work, facilitates greatly the application of the nanocrystals in device fabrication.