It takes 21 days for a chicken embryo to develop. Ever wonder what happens inside the egg between the day it's laid and the day the chick pecks its way out?
You're in luck. Thanks to YouTube video poster Poultry CRC, you can see every stage of the chicken embryo's development. The video -- animated so you don't have to see any cool-but-gruesome images of partly developed chicks -- is fascinating stuff.
Tissue starts forming on the yolk by the end of the first day, and by day two the heart is formed. By day eight, the beak and feathers are visible. On the 21st day, the chick finishes its escape from the shell, making its first "external pip" and finally entering a new environment.