When hen lay egg its yolk is clean and yellow in colour..

After a few days the generation of a chick starts and a clot of blood appears in the yolk ....

The blood clot starts growing .....

with in a week an embryo forms....

The embryo starts growing and gets required nutrients from the egg white...

it keep on growing ...

a time reaches when the embryo appears to be chick...

After 21 days a new born chick breaks egg wall and comes out.....