Publisher Summary Sphingolipids are found in all animals, plants, and fungi, and in some prokaryotic organisms and viruses. They are composed of an sphingoid base backbone to which a fatty acid may be attached through an amide bond and a head group at the primary hydroxyl. The head groups range from a simple hydrogen to more complex species, such as the phosphocholine moiety of sphingomyelin (SM) and the simple to complex glycans of glycosphingolipids. Sphingolipids function as structural components of membranes, lipoproteins, skin, and other biomaterials, and as cell signaling modulators and mediators. Sphingolipids tend to associate with each other as well as with cholesterol and certain categories of proteins, such as those attached to the membrane via a glycosylphosphatidylinositol anchor. The aggregates are genetically referred to as “rafts” unless they can be more specifically defined by co-localization with a marker for a distinct membrane structure, such as caveolin for caveolae. Rafts are envisioned to be relatively small, distinct, and liquid-ordered subdomains of the plasma membrane that form and disperse rapidly due to the highly saturated alkyl chains and intermolecular hydrogen bonding of sphingolipids.