This book discusses the paradigm-shifting phenomenon of intrinsically disordered proteins (IDPs) and hybrid proteins containing ordered domains and functional IDP regions (IDPRs). The properties of IDPs and IDPRs are highly complementary to those deriving from the presence of a unique and well-defined three-dimensional fold. Ignored for a long time in high-resolution studies of proteins, intrinsic protein disorder is now recognized as one of the key features for a large variety of cellular functions, where structural flexibility presents a functional advantage in terms of binding...