Day 1 : Fertilization 

• In the race - Hundreds of millions of sperm go in search of the egg immediately after ejaculation.
• Only one winner - First sperm to reach the egg and fertilize it.

Day 2 to 4 : Zygote to morula 

• Zygote - Resultant cell from the union of the sperm and egg.
• Formation of morula - Zygote goes through stages of cell division. While it travels through the fallopian tube, it undergoes cell division and reach the stage of 16 cells, at which point mulberry shaped cell called morula is formed.

Day 9 : Morula to blastocyst and implantation

• Formation of blastocyst - After cellular division to 64 cells, the morula becomes a blastocyst, a more compact and solid mass.
• Implantation - After the formation of blastocyst, it implants itself in the uterine wall 9 days after fertilization.
• After implantation, the embryo begins to grow.

Day 10 

• The placenta forms - After plantation, placenta begins to grow. Placenta is a sharing organ between embryo and mother through which blood, food and water is supplied to embryo.

Day 19 

Organ foundation - After different cell migrations and their installation in specific places, the foundation is laid for the internal construction of a new being.

• Neural tube has acquired its shape and will be key in the formation of the nervous system.
• The heart is in its place and in a few days will begin to beat.

Day 22 - C shape

Length - 4 mm (0.2 inches) & Weight - 0.03 grams

• Liver and kidneys begin to form. The first two months of gestation, the liver is the central organ for blood production.
• Formation of the eye.
• The heart begins to beat - By day 22, the heart becomes active.
• Development of the heart - After the differentiation of the cells that form the blood vessels, the cardiac muscles appears and begins to pump with the beating of it cells.

At this stage, 50% of the embryo is composed of just two organs : the brain and the heart.

Day 36

Length - 10 mm (0.4 inches) & weight - 0.05 grams.

• Small buds begin to appear that will grow until they form the arms and legs.

Day 40

Length : 10 mm (0.4 inches) & weight - 0.1 grams

• Changes in the head - The brain begins to develop and produce growth hormone and others.
• formation of face - Jaw and facial muscles begin to develop.
• External ear starts to grow.

Journey of a baby is very exciting to know. Isn't it? We will continue it in thee next blog…