Many humans consume various types of eggs as part of their diet. Two edible parts of a chicken egg (the type most often consumed) are shown here: the white and the yolk. The white is a clear liquid surrounding the yolk, consisting of 90% water and 10% dissolved proteins. The yolk, a firm yellow sphere, contains all of the egg's fat and cholesterol and about one-half of the protein. Not shown in the illustration is the egg's outer shell which is not normally consumed.Photo: Biswarup Ganguly