The book "Tight Junctions" offers a comprehensive analysis of the role of tight junctions (TJs) in epithelial and endothelial cells. These cell-cell adhesion structures are crucial for the formation of separate compartments in multicellular organisms and for the exchange of substances between the internal environment and the external surroundings. The perception of TJs has evolved over the years; they are no longer viewed merely as static barriers, but as dynamic structures that adapt to physiological, pharmacological, and pathological challenges. The book highlights the diverse functions of TJs, which extend beyond limiting membrane movement and also involve the regulation of cell proliferation. These insights are of great significance for the development of effective strategies for treating diseases such as cancer and autoimmune disorders. The chapters of the book reflect this expanded perspective and are based on the identification of a variety of proteins that are integrated into the structure of TJs.