Keratins represent a group of fibrous proteins produced in some epithelial cells of vertebrates such as reptiles, birds and mammals. These proteins are abundantly present in nature and they constitute the major part of hair, wool, horns, nails, feathers and stratum corneum of the skin. In this book, the authors present current research in the study of the structure, properties and applications of keratin. Topics discussed include simple epithelial keratins K8 and K18; extraction, processing and applications of wool keratin; water sorption of human keratinised fibres and keratin expression in the human pituitary gland and its application to neoplastic pituitary cells.