Tight junctions that connect endothelial cells of blood capillaries have usually a less complicated organization than those of other epithelia. The networks of junctional strands in these junctions are sparse while there are intervals between the strands; so it is relatively easy for molecules to move through the intercellular spaces. The permeability of endothelial lining is high enough not only for ions and minute molecules but also for proteins like albumin. Tight junctions are dynamic structures where the network complexity for adhesive strands (junctional fibrils) and, thus, their permeability is regulated according to functional needs. We may assume that one of these fibrils, in the bottom right corner is undergoing such reconstruction.