Things you probably never knew, such as:
"Chicks, when they start to hatch, first break through the membrane to practice breathing. You know that pocket of air on the big side of the boiled egg? That's what that is for. Breathing practice.
After the chick breathes up that pocket of air, they break through the shell to let more air in. The chicks have a special little "tooth" on their beak they use to do this."