The curved shape of an eggshell protects against damage, while inner membranes ensure that even if the shell is cracked, it may still stay intact. An eggshell is made up primarily of calcium carbonate crystals, which provide solidity without being brittle.
The shape of the eggshell has long been used in architecture; for instance, it can be found in the pointed Islamic or Visigothic Arch. The curve at the top of an eggshell is shaped in such a way that it takes a large amount of force to break it. However, if the force is applied to the sides of an egg shell, it will break easily.