This book addresses the structural and biological properties of the extracellular matrix component and glycosaminoglycan polymer hyaluronan (or hyaluronic acid, HA). The book discusses various aspects of HA biology, e.g., HA synthesis and degradation, as well as the role of HA in embryogenesis, development, and cell maintenance. The reader will learn about the role of HA in different tissues as well as its biological activities triggered by the interaction with different HA receptors. A closer look is had at the involvement of HA in human pathologies such as cancer, kidney fibrosis and wound healing. Biotechnological and biomedical applications for HA such as scaffold generation and drug delivery, including the novel synthetic sulphated HA are explored. This work will appeal to a wide readership within the extracellular matrix and hyaluronan field. It can serve as an introduction to the field for junior scientists but can also help senior scientists to gain a broader view of the field beyond their area of specialization. The series Biology of Extracellular Matrix is published in collaboration with the American Society for Matrix Biology and the International Society for Matrix Biology.