In recent years, polyhydroxyalkanoates (PHAs), the only family of biopolyesters completely synthesized by biological means, received increasing attention because of their attractive properties and wide applications. PHAs and their related academic and industrial chains have affected our daily lives in fermentation, materials, feeds, energy as well as in the medical fields. It is very important to understand all aspects related to the PHAs their processes in this valuable field. This book presents a general overview of PHAs from the biosynthesis, fermentation, industrial production, extraction, purification and application. This book consists of four sections including 21 original chapters, which together provide a comprehensive introduction to the subject, and the detail information for the biosynthesis, industrial production, and medical application of PHAs. This book is written to be accessible to a wide readership, especially for beginners who have just started PHA related research. In a word, this book summarizes the literature data and recent research results on PHAs with a state-of-the-art description of the present, challenge and future of PHAs.