An egg is composed of a brown or white outer shell, consisting primarily of calcium carbonate, that contains seven interior elements. The shell color does not affect the thickness of the shell nor the quality, flavor, nutritive value, or cooking characteristics of the egg but is determined by the breed of chicken that produced it. Eggs stand alone as the most versatile and nutritious food given to mankind. One large egg contributes approximately 6.5 grams of protein (or about 13 percent of the average adult’s minimum daily requirement), as well as substantial amounts of iron, choline, thiamin, phosphorus, and the vitamins A, D, and E. The yolk contains most of the fat, cholesterol, vitamins, and half of the protein while the white, also known as the albumen, is composed almost entirely of water and proteins called albumins. It also contains niacin, riboflavin, and minerals. The most common eggs used today are those of chickens, although turkey, goose, duck, and quail eggs are also sold.