Vascular permeability is a research area within the field of physiology and pathology that focuses on the regulation of blood vessel permeability in the body. Blood vessels are lined with endothelial cells that control the passage of substances such as nutrients, water, and immune cells between the bloodstream and surrounding tissues. Abnormal changes in vascular permeability can lead to conditions such as edema, inflammation, and cancer metastasis. Researchers in this area investigate the mechanisms that regulate vascular permeability, the role of various signaling pathways and molecules in this process, and potential therapeutic targets for controlling blood vessel permeability in diseases.