Molecular recognition is a mature branch of chemical science, and why shouldn't it be? Decades of studies in physical organic chemistry have defined and evaluated the weak intermolecular forces involved when 2 molecules encounter each other. Every bimolecular reaction, whether it occurs in the gas phase, dilute solution, or an enzyme's interior, begins with a recognition event. It is an apt time to explore recognition in a larger context, that of multicomponent assemblies, and this special issue of 14 contributions is a beginning Molecules can be made to self-assemble spontaneously into multicomponent, complex structures when they are instructed to do so. The instructions exist in the form of the molecule's shape, its chemical surfaces, and how well it fills space in the phase where the assembly takes place. These instructions are written into the molecule during its synthesis. Each step in the assembly process is reversible and dynamic: the complex product is constantly forming and dissipating, and this feature allows for the correction of errors as the assembly proceeds. Self-assembly implies the distinction between “self” and “nonself,” with recognition and selection between the two during assembly. When 2 different self-assemblies are in the same solution they may coexist and remain self-sorted or they may hybridize. This molecular miscegenation occurs when one component prefers to interact with a component other than itself. You can share your ideas & comments further at : molecularbiology@scholarlymed.com molecularbiology@scholarlymed.com