Recently, it has been discovered that crystalline organic thin films can be deposited in nearly single crystalline form on a variety of substrates such as glass, polymers, etc. Since then, this discovery has led to the growth of crystalline organic quantum wells, waveguides, coupler/switches, and organic/ inorganic heterojunction devices such as field effect transistors and avalanche photodiodes. Organic light emitting diodes (LEDs) which luminesce in the red, green and blue have also been demonstrated. In this paper, we will report on several recent advances in the growth of organic thin films deposited by organic molecular beam deposition. We report on modeling of organic monolayer growth based on the atom-atom potential Method. The Model provides insight into the factors which control “quasi-epitaxial growth” i.e. the ordered growth of one layer of an organic film which is incommensurate with the substrate lattice. We also observe large optical nonlinearities which are a feature of both single and Multi-layer crystalline organic films. The growth of organic, nonlinear optically active crystalline organic compounds are also discussed.