This book arose from a conference organized under the auspices of the Australian Research Council’s Complex Open Systems Research Network (which has become the most prominent for complex systems in the world — just Google “complex systems network”), the ANU Centre for Complex Systems, and the Asia-Pacific Center for Theoretical Physics. The book is unique in the scope of its coverage of applications of complex systems science: Extraterrestrial — astrophysical, solar and space plasmas; Earth System — climate, ecosystems; Human systems — brain dynamics, social networks, financial statistics, advanced technologies.It also presents up-to-date discussions of new theoretical approaches, in particular those based on entropy and entropy production maximization, a field still under development but with much promise for providing a much-needed unifying principle for complex systems science.The authors are at the forefront of their fields, and organized their chapters to effectively bring out common features of complex systems. A comprehensive and common lexicon of keywords has been used to unify indexing, thus making the book an invaluable introduction to anyone seeking an overview of complex systems science.