How to cells undergo differentiation to form the numerous types of cells in the body?

Cell differentiation is how generic embryonic cells become specialized cells. This occurs through a process called gene expression. Gene expression is the specific combination of genes that are turned on or off (expressed or repressed), and this is what dictates how a cell functions.

The stem cells that are initially formed in the body undergo differentiation through various chemical signals that drive them to differentiate into appropriate cell types.

Explanation:

The two haploid gelametic cells fuse to form a diploid cell which is got as a zygote. This zygote is a simple cell that undergoes repeated mitotic divisions to form different cellular organelles.

The cells that are differentiated into a particular type thereby they are differentiate into different organ systems according to the chemical signals that are received by the receptors of the cell.