Scientists solve eggshell mystery of how chicks hatch

A freshly hatched chick rests after strong efforts to break through its egg. Photograph: Michael Probst/AP
It’s been a tough one to crack, but scientists say they have zoomed in, to an unprecedented degree, on the structure of shells surrounding chicken embryos, revealing how they change to allow young birds to hatch.
Before being laid, bird eggs form a hard calcium-rich shell with three main layers. While it was already known that these thin from the innermost out as a chick grows in preparation for hatching – with calcium from the shell being incorporated into its skeleton in the process – quite what happens at the molecular scale has been something of a mystery.