A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids. As a blood lipid, it helps enable the bidirectional transference of adipose fat and blood glucose from the liver. There are many triglycerides: depending on the oil source, some are highly unsaturated, some less so. Saturated compounds are “saturated” with hydrogen — all available places where hydrogen atoms could be bonded to carbon atoms are occupied. Unsaturated compounds have double bonds (C=C) between carbon atoms, reducing the number of places where hydrogen atoms can bond to carbon atoms. Saturated compounds have single bonds (C-C) between the carbon atoms, and the other bond is bound to hydrogen atoms (for example =CH-CH=, -CH2-CH2-, etc.). Unsaturated fats have a lower melting point and are more likely to be liquid at room temperature. Saturated fats have a higher melting point and are more likely to be solid at room temperature. Triglycerides are the main constituents of vegetable oil (typically more unsaturated) and animal fats (typically more saturated). Triglycerides are a major component of human skin oils.