The Pip That Breaks the Shell

Around day twenty-one inside a chicken egg, something extraordinary happens. The chick — heart beating, lungs ready, feathers formed — faces the most critical moment of its brief existence. It is fully alive, but sealed inside a calcium shell. If it remains there, it will suffocate despite being perfectly viable. So the chick pips. Using a small, hard nub called an egg tooth — a structure it will lose within days of hatching — it taps and cracks the shell from the inside out.…