Number one, we'll always find a platform molecule, a molecule that acts as the backbone of attachment for the other groups, in the case of the phosphoglycerides will have a glycerol that acts as a backbone. In the case of the spingolipids, will have a slightly different platform molecule known as a spinocine. Now, they always have fatty acids. In the case of spingolipids, we have one fatty acid. In the case of phosphoglycerides, we have more than one fatty acids. They always contain a phosphate group.