Vitamin A is an essential fat-soluble vitamin. Fat-soluble vitamins (A D E and K) are stored within your fat resources, while water-soluble vitamins are stored within the water resources of your body. As a result your body can live from vitamin A resources you ate 2 weeks ago. Vitamin B resources for example have to be refreshed all the time. The bad side of this is that you can poison yourself eating too much vitamin A. For information about other vitamins go to nutrition main. Everybody knows that vitamin A is good for the eyes, but it is also required for the immune system, protein synthesis, bone metabolism, etc.