The mitosis is an interesting process, in which we have a type of cell division were the end result is two identical daughter cells, both of which have the same amount of chromosomes as the parent cell.
This process can be found in the growth of the tissue.
The process of mitosis can be seen as a sort of cellular immortality because the cell is able to divide itself, thus create two identical cells from itself. Those two cells are able to do the same, and they can constantly double and create more and more cells that identical to them, which in a way comes as an extension of the life of the initial parent cell all the way.