Day 1 - Today our chicks develop tissue Day 2 - Chicks will develop a heart which will beat for the first time Day 3 - Chicks begin to develop blood vessels. Day 4 - Today our chicks will develop limbs. The egg will develop wings, legs, brain, and eyes. Day 5 - Chicks develop their elbows and wings today. Day 6 - Today our chick will develop digits for its beak. Day 7 - Chicks will develop its beak, egg tooth, and comb. Day 8 - Feathers and feather tracks will begin to develop today.