This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book deals with the problem of the design and management of complex systems. It aims to develop a generalized approach to system development, such that the chaos which inevitably ensues can be controlled. In order to develop the simplest solution to a complex problem, the problem must be well understood. Thus, a central concern in the development of complex systems is understanding. Like many complex systems, early spacecraft were relatively simple. However, especially after the advent of the computer, spacecraft have become increasingly complex. The design and management of complex systems involves the execution of technical activities together with managerial activities. Most anyone who has been involved in the development of a complex system has been struck by the amount of chaos that can develop so quickly.