Lipocalins are a large and diverse group of small, mostly extracellular proteins that are found in vertebrates and invertebrate animals, plants, and bacteria, and include invertebrate colourant proteins, such as lobster crustacyanin, rodent pheromone transport proteins such as α₂-urinary globulin, various clinically important human plasma proteins (including retinol-binding protein, α₁-acid glycoprotein, and α₁-microglobulin), ruminant milk β-lactoglobulin, the brain enzyme prostaglandin D synthase, as well as all important mammalian aeroallergens, such as Bos d 2 or Can f 1. We explore the current naming conventions of some lipocalins, and briefly outline the known physical properties of lipocalins.