An eggshell is the hard, outer covering of an egg, primarily composed of calcium carbonate. It serves as a protective barrier for the developing embryo inside, providing both strength and a degree of flexibility. The thickness and texture of eggshells can vary among different species, such as chickens and quails. Eggshells are typically white or brown, depending on the breed of the bird. They also contain tiny pores that allow air and moisture to pass through, which is essential for the embryo's growth. After the egg is laid, the eggshell remains intact until the chick hatches, completing its development.