between dissimilar materials is facilitated by a structural interdigitation of fibers into each mammillae at the microscale, and reciprocally, at the nanoscale, mineral spiking into fibers directly at the interface

While the bulk of eggshell is made of calcium carbonate, it is now thought that the protein matrix has an important role to play in eggshell strength. These proteins affect crystallization, which in turn affects the eggshell structure. The concentration of eggshell proteins decreases over the life of the laying hen,