This volume attempts to provide a synthetic view of fundamental theoretical physics. It describes the ingredients which may have to be used in order to build a theory which will unify general relativity, quantum field theory, and the known fundamental interactions. This book provides enough detail to start with, but does not go too far in developing a particular special field. Instead it turns to another special field and then shows how different fields are interrelated in a fascinating way. Many surprising new findings are revealed. This book should be of interest to those who would like to explore how the "Theory of Everything" could possibly be formulated. It should also be of interest to researchers and students. A background in general relativity and quantum mechanics is recommended. The introductory sections, and especially Part IV: Beyond the Horizon, need no such background knowledge. They are intended for the reader who is interested in the conceptual and even philosophical questions.