This volume explores the dynamic topic of tight junctions. The book focuses on tight junctions' role in sealing adjacent epithelial cells in a narrow band just beneath their apical surface. The book explains how tight junctions consist of a network of claudins and other proteins, and delves into how they hold cells together and form functional and protective barriers, regulating the passage of molecules and ions through the space between cells. The book opens with a discussion of the evolution of research on tight junctions, discussing a range of primary areas of growth, including the current knowledge on the particular physiological function of different claudins due to the development of an array of knock out mice. The chapters also explore in-depth studies of tight junctions in specific tissues (gut, lung and endothelia). This book offers a comprehensive understanding on post-translational modifications of occludin and its impact on tight junction function, as well as the molecular composition and function of tricellular tight junctions. This volume is particularly relevant to students and scientists in neuroscience, cell biology, physiology, cell differentiation, and cancer research.