In this talk, I will describe the basic physics behind the molecular ordering at interfaces in a variety of organic systems. The crystallinity, the morphology, and the associated patterns formed in functional organic films are found to play a critical role in the performances of molecular-based devices such as liquid crystal displays, organic electroluminescent displays, organic thin-film-transistors, and biosensors. In contrast to conventional inorganic solids, the interfacial ordering at a molecular level, on a nano-scale order, will propagate easily into the bulk and predominantly govern the macroscopic physical properties of functional organic films in the presence of the surface modification. Based on the concept of the molecular ordering at interfaces, common features of the molecular devices will be discussed.