This book provides state-of-the-art insight into Tight Junctions (TJs), the intersection of epithelial and endothelial cells in various tissues. Opening with an analysis of the evolutionary development of a transporting epithelium in early metazoans, the book describes current understanding of TJ structure and function information, including evidence supporting the presence of ion channels within TJs. Also deals with TJs of central nervous system myelin and at the blood brain barrier.