Eggs are naturally shaped to fit snugly together in a cup-shaped nest, with a more upright orientation rather than a flat position. Their strength primarily lies along the long axis of the egg. Since birds are lightweight creatures, the portion of their body that rests on the eggs, their abdomen or tummy, is soft and helps keep the eggs warm without causing them to crack.

Throughout evolution, eggs have developed a balance of strength that is not excessively strong. This is because birds need to have a weak spot on the shell through which they can peck their way out when it’s time to hatch. The eggs are further reinforced by a thin outer “varnish” layer on the shell and a delicate inner membrane, both of which serve as barriers against harmful bacteria.

It’s worth noting that in British and European food processing practices, the thin outer varnish on eggs is left intact. This allows eggs to be stored without refrigeration for extended periods. On the other hand, the American approach of thoroughly cleaning the egg surfaces necessitates refrigeration from the beginning, as without it, they would spoil quickly. Eggshells have some degree of porosity, allowing for gas exchange