Ceramides are colorless, transparent, liquid, water-soluble lipids that regenerate keratin regularly, promote cellular metabolism, and conduct cellular messages. The components of the stratum corneum with their lipid content are 50% ceramides, 30% free fatty acids, 15% cholesterol, and 5% cholesteryl esters. Ceramides are the most abundant and play the most important role in the entire stratum corneum. It plays an important role in preventing moisture from escaping and in protecting against external stimuli. It protects, moisturizes, and hydrates the skin, and it is contained in all skin care products used on a daily basis.