In 1929, famous Danish chemist Dame first discovered and extracted a yellow crystal substance vitamin K from animal liver and sesame seed oil. Vitamin K can be divided into two categories, which are 2-methyl-1,4-naphthoquinone derivatives. One category is fat soluble vitamins, namely, vitamin K1 extracted from green plants (such as alfalfa, spinach and other green leafy plants) and vitamin K2 extracted from microorganisms. Human intestinal bacteria (such as Enterobacter coli) can also synthesize vitamin K2. Vitamin K1 is yellow oil, K2 is light yellow crystal, all have heat resistance, but easy to be damaged by ultraviolet radiation, so it should be kept away from light. The other is water-soluble vitamins, which are synthesized artificially, namely, vitamins K3 and K4. The most important are vitamins K1 and K2. Vitamin K is an oily liquid or solid, insoluble in water, soluble in oil, ether and other organic solvents, with stable chemical properties, heat and acid resistance, but easily decomposed by alkali and ultraviolet. Vitamin K is an important vitamin for promoting blood coagulation and bone growth. Dark green vegetables and yogurt are easy to get vitamin K supplements in daily diet. The vitamin K requirement of human body is very little, but it is to maintain the normal coagulation of blood function, reduce a lot of bleeding in physiological period, and prevent internal bleeding and hemorrhoids. People who often have nosebleed should take more vitamin K from natural food.