The present article aims to provide a theoretical foundation for the evaluation and categorization of the knowledge domain of Chain and Network Science (CNS). It aims to clarify what the field of CNS includes and to investigate where we stand in developing CNS. It elaborates on a number of important theories that provide insight in the structure and activities of actors in chains and networks, and discusses the key issues that are raised by each theory. It concludes by suggesting some important research questions in the field of CNS, integrating the different theoretical perspectives, and touching upon a number of management challenges for the years to come.