Lycopersicon esculentum lectin (LEL or tomato lectin, TL) is a single-subunit glycoprotein containing arabinose and galactose and may form multimeric aggregates in solution. Although it shares specificities with potato lectin, Datura lectin, and wheat germ agglutinin, LEL is dissimilar in many respects. It binds well to glycophorin and Tamm-Horsfall glycoprotein, has been used to label vascular endothelium in rodents, and is an effective marker of blood vessels and microglial cells in rodents. Conjugation with a fluorophore facilitates fast, one-step detection and visualization using intravascular perfusion methods or direct application to tissue sections. This fluorescein-labeled LEL features a ratio of fluorophores to lectin protein that provides optimal staining (excitation 495 nm, emission 515 nm). Supplied as a solution essentially free of unconjugated fluorophores, it is preserved with sodium azide. The recommended inhibiting/eluting sugar is chitin hydrolysate.