This chapter introduces the collective monograph Navigating Complexity in Big History – Exploring Periodization Across Cosmic and Biosocial Dimensions that explores the aspects and proposals for periodization of Big History in the context of complexity and some other important directions as a navigation and compass in various processes, trends, fluctuations, etc., in the past, present, and future of Big History and humankind’s destiny. This volume is unique because it brings together a wide range (but not all) of approaches to Big History periodization, something not done before. This introductory chapter provides an overview of issues related to the idea that periodization is a very effective method of analyzing and organizing material because it opens the opportunity to see a complex picture of the development and growth of complexity in Big History. The procedure of periodization in Big History suggests a way to explore complexity growth across cosmic, biosocial, and social dimensions. The chapter places the effort of periodization into historical, modern, and future context along with complexity science considerations. The various frameworks offer different bases such as combined measures of complexity, information and combinatorial mechanisms, and patterns of dynamical evolutionary systems. Presented periodizations allow readers to see the multifaceted nature of Big History, the various correlations in its course, to see more clearly its certain phases and—especially—different approaches to interpreting this history and its individual phases. The introductory chapter also provides a reader with some important terms such as complexity, information, energy, organization, environment/limits, and others which also can be used as a criteria of Big History's periodization. This chapter also introduces a reader with the book organization and main ideas of the contributors. So, the combination of complexity and periodization is able to describe and explain many different processes and transformations.