Vitamins are generally classified into two groups based on their solubility: fat-soluble vitamins and water-soluble vitamins. Vitamins A, D, E, and K are fat-soluble, meaning they dissolve in fats and oils and are stored in the liver and adipose (fat-storing) tissues. The Vitamin B complex (such as B1, B2, B6, B12, etc.) and Vitamin C are water-soluble vitamins. They dissolve in water and are generally not stored in the body (with the exception of Vitamin B12), so they must be continuously supplied through the diet.