Vitamins are nutritional compounds needed by all organisms in their diet. Vitamins do not include essential nutrients like dietary minerals, fatty acids, or amino acids. Vitamins are catagorized by what they do rather than what they are. Many vitamins are actually several vitamins that share characteristics like vitamin A which includes retinal, retinol, and carotenoids. Vitamins are very diverse and often play other functions as biochemicals like hormones, antioxidants, and cell mediators. Vitamins also play a role in tissue growth and the brain. The vitamin B's are the largest group of vitamins, they help metabolisms. Vitamin intake can vary greatly in the diet due to simple things like rain and soil, if vegetables are eaten that were grown in vitamin rich soil then the vegetables them selves are vitamin rich. And the same goes for nutrient lacking soils. Not untill the 1900's were vitamins able to be controlled in the diet by use of supplemental pills. Before the 1900's people depended on food that was grown in nutrient rich soils or animals that were feed foods that were grown in nutrient rich soils. Vitamin supplements have become widely used and marketed. Multi supplements containing vitamins have become cheaper and cheaper over time. The ancients Egyptians long before vitamins were discovered feed liver to patients suffering from poor eye sight at night. We now know this is due to a vitamin a deficiency. In 1749, James Lind found that citrus fruits helped prevent scurvy. Scurvy is a deadly disease where collagen is not formed properly, causing slow wound healing, bloody gums, imense pain, and eventually death. Vitamins can either be water-soluble or fat-soluble like most things in the world. For humans there are 13 vitamins. 4 vitamins are fat-soluble these vitamins are vitamin A, vitamin D, vitamin E, and vitamin K. The 9 water-soluble vitamins are the 8 B vitamins and vitamin C. Most water-soluble vitamins are excreted in urine and are not stored by the body, thus daily intake of these vitamins is crucial. Fat-soluble vitamins are absorbed through the intestines by fatty lipids and are more likely to accumulate in the body. Vitamins are critical compenents of life, without them life could not digest food, process food into energy, or use that energy. Vitamins also play a big role in reproduction.