The development of the chick starts in the single cell formed by the union of two parental cells, egg and sperm, in the process known as fertilization. In birds, fertilization happens around 24 hours before the egg is laid.
At the time of laying, many cells are gathered in a little, whitish spot (the blastoderm or germinal disc) that is observed on the surface of the yolk.
At the point when the egg is laid and cools, division of the cells stops. After the egg is laid, cooling the egg after the egg is laid does not bring about the death of the embryo. It might continue its development following a few days of rest on the off chance that it is again warmed by the hen or in a hatchery.
Special temporary organs or embryonic layers shaped inside the egg, both to protect the organism and to provide for its nutrition, respiration, and excretion. These organs incorporate the yolk sac, amnion, and allantois.
The yolk sac supplies, food material to the embryo. The amnion, by encasing the embryo, gives protection. The allantois fills in as a respiratory organ, gets minerals from the shell, and handles waste. These brief organs work inside the egg by the time of hatching.
A few changes occur during the 18th and 21st days. The chick draws what remains of the yolk in its body when it hatches. The chick’s head is under its right wing to the tip of the nose pointed at the air seal. The huge neck muscle contracts and forces the egg tooth through the air cell, and the chick takes its first breath. This is known as interior piping.
On the twenty-first day of brooding the chick completes its escape from the shell. The egg tooth makes the initial break in the shell. This is known as exterior piping.
The incubating process can last from 4 to 12 hours before the chick breaks free from the shell. The chick, as it shows up after liberating itself from the shell, is wet and exceptionally drained. For the following a few hours it will lie still and rest. A couple of hours later the chick, now dry and soft, will turn out to be extremely active and the egg tooth will get and fall dry.