This book provides an up-to-date overview of the architecture and biosynthesis of bacterial and archaeal cell walls, highlighting the evolution-based similarities in, but also the intriguing differences between the cell walls of Gram-negative bacteria, the Firmicutes and Actinobacteria, and the Archaea. The recent major advances in this field, which have brought to light many new structural and functional details, are presented and discussed. Over the past five years, a number of novel systems, e.g. for lipid, porin and lipopolysaccharide biosynthesis have been described. In addition, new structural achievements with periplasmic chaperones have been made, all of which have revealed amazing details on how bacterial cell walls are synthesized. These findings provide an essential basis for future research, e.g. the development of new antibiotics.