The hen's egg plays a crucial role in the embryonic development of the bird. It serves first as a source of energy and nutrients of high digestibility and, second, protects the embryonic bird against external aggressions. The unique structure of an egg with yolk containing the embryo surrounded by albumen and shell as physical barriers, is the first element of this protection. The second one consists of the specific composition of yolk, albumen and shell with many molecules possessing elevated biological properties. Thus, these molecules represent a major source of active principles usable by medical, pharmaceutical, cosmetic, nutraceutical and biotechnological industries. In this review, we will focus particularly on nutritional, health, and biotechnological activities of egg molecules and on the approaches, which are proposed by European research groups, to exploit this bioactive potential.