Triacylglycerols (TAGs) are esters derived from a glycerol and three fatty acid molecules. The simplest TAGs are those with three identical fatty acids. The length of the fatty acids of TAGs can range from C4 to C24 carbons, but the most common are C16, C18, and C20. Fatty acids can be saturated or unsaturated. Natural fatty acids found in plants and animals typically consist of even numbers of carbon atoms because they are biosynthesized from acetyl-CoA with two-carbon units.