Nature is amazing and always has tricks. We know that our body is made up of trillions cells divided into about 200 types. How can a single cell be divided that fast from 1 to trillions, and besides they are divided into various types? That is what scientists say. Is that cell called SUPER CELL? No, so what kind of cell is that?

what is the 1st cell we all are made from?

When a couple have an intercourse, the woman could have her egg (female sex cell) penetrated and fertilized by a sperm (male sex cell) from her partner. The fertilized egg, which is formed from the merging of one egg and one sperm, is called Zygote. That cell is the one we all are made from. Some consider it as a single-cell organism. This cell starts dividing and replicating itself again and again; within a few days it divides to about 100 cells, and it is called “blastocyst” the earlier embryo stage. These cells are known as embryo stem cells, and they will differentiate to different type of cells for different tissues and organs at a stage called “differentiation”.

Cell differentiation stage?

The cell differentiation is the stage when the stem cells start to divide themselves into different type of cells such as for heart, skin, nerve, etc. The earlier sequence of this differentiation is called “gastrulation”, in which the first distinct tissue layers are formed. See the enclosed picture for the development from the zygote to different cells in the gastrulation. 
 
What triggers the differentation stage?

The main question here is what triggers these stem cells to differentiate to various types of cells, which form different tissues and organs in well coordinated manner. That is what the scientists are studying and researching; yet they are in a long way to understand it. However at this point they believe:
Genes in DNA play a big role in this cell differentiation.

Genes are activated differently for different cells.  Scientists mean that the genes are activated (turned on or off) differently for heart, liiver, and muscle even though they are all have the same DNA and genes.

Will scientists be able to understand the genes and this process?

My put would be yes. They just need time. Currently they attempt to map all the human genes (20,000-25,000), while some scientists do some stem cultures and attempt to find out what cause cells activated differently than others with well coordinated manner. But again they are in a long way to understand it.

What are DNA and Genes?

They are not in the scope of this essay, thus they are not covered in detail. Our body is made up of trillions cells divided into various types of cells. Each cell of any type has the same chromosomes (23 pairs), which reside in the nucleus of the cell; the nucleus is in the center of the cell.  Each chromosome contains a different strand of DNA (Deoxyribonucleic Acid), and each DNA is composed of genes. Scientists estimate that human being may have 20,000-25,000 genes. Note that we all have different DNA except the identical twins.