Growth in most in organisms is caused by nuclear cell division.
The chromosomes containing dna first replicate-in humans, the 46 chromosomes in cell double.
The cell then divides in a series of steps resulting in 2 new cells that each have the original chromosomes, or the exact copy of the original.
Through this process, new cells are made, for example, to form a scar after an injury, new bone cells, muscles cells, blood cells, and any cell that is needed in the body throughout life and growth.
In single-celled organisms, this process is the cell's form of reproduction-making exact copies of the dna in each of the 2 daughter cells, and is ofter called binary fission.this type of reproduction is also called a sexual reproduction because only one organism(the single cell) is involved and there is no exchange of genetic material or dna. Thus, the 2 offspring cells, or daughter cells, are identical to the original or parent cell.