Astonishing progress has been made in recent years to understand the structural complexity and functions of the biosynthetic pathways of the bacterial and archaeal envelopes. This progress has prompted me to assemble the present book that provides a detailed overview and the state-of-art of the respective research field. Ideally, the book will provide students and advanced scientists an up to date picture of the different parts of the bacterial and archaeal cell envelope and enable them to understand their functional roles.