Crystals of organic compounds, the final supramolecular and solid state molecular recognition and its assembly, chemical and geometric factors, from a single molecule is the best example. The description of the crystal structure of the implicit supramolecular crystal molecule is maintained by non-covalent bonding interactions facts together. Aimed at understanding the phenomenon of intermolecular interactions and identify the context of crystal packing, crystal engineering, you need a reasonable method of solid-state structure of basic and practical significance. Of crystal engineering purposes, it is the interaction between the molecules on the basis of reliable connection is established between the molecular and supramolecular structures. Ideally, would like to identify the target of the sub-structural unit, the supramolecular assembly of the precursor molecules that can be selected from the logic. In fact, the crystal engineering is a new organic synthesis, the purpose of this article is to show rather than name only organic chemistry, this problem is the concept of mainstream, traditional organic synthesis are surprisingly similar. The details of each is not the same, because one here deal with the interaction between molecules, rather than a covalent bond, so the article is divided into two parts. The first is to focus on strategic relationship between the prominent crystal engineering and organic synthesis concept and introduced the term supramolecular synthon. Emphasized second portion, i.e., a specific molecular interaction between the chemical and geometric properties.