This book aims to give an introduction to the theory foundations, various sub-fields, current research status and practical methods of software architecture. In this book, readers can acquire the basic knowledge of software architecture, including why software architecture is necessary, how we can describe a system's architecture by formal language, what architecture styles are popular for practice use and how we can apply software architecture into the development of systems. Study cases, data, illustrations and other materials which are released in the recent years will be used to show the latest development of software architecture. This book can be used as the learning material for touching software architecture.