The avian egg is one of the richest and most balanced sources of nutrients among all of the foods available to mankind. Its biological function is to support the development of the embryo from fertilization to the emergence of the newly hatched chick. The structure of the egg is such that it maintains an aseptic “milieu” for embryonic development. It protects the embryo from physical trauma, allows for the exchange of respiratory gases between the embryo and the environment, and provides the embryo with all of the nutrients that are needed for growth and development. Eggs are generally similar among species of birds, but they can differ in some aspects of their physical and chemical composition. This article briefly describes the physical structure, chemical composition, and nutrient content of the egg of the chicken, Gallus gallus domesticus.