Here’s the reality: every single cell in the body originated from what’s called a totipotent stem cell. That’s the cell that’s created when the egg is fertilized by sperm. That gives rise to the development of the embryo, and the embryo gives rise to the development of the placenta and the fetus. All of these things contain within them a whole population of stem cells which go on to mature and specialize into all the different cell types of the body.
There is a process called renewal, where during each cell division, the stem cell actually makes a copy of itself along with a copy that goes through the process of differentiation. Now, this cell division process can be either asymmetric or symmetric. In some cases, the stem cell population simply wants to make more versions of itself, and that’s a symmetric cell division where it makes two perfect copies of two stem cells. In other cases, it will make a copy of itself, and it will give rise to another cell, which actually goes through a process of differentiation, and starts to mature and specialize. So do they renew themselves and make more of themselves? Absolutely! They do copy themselves and make more of themselves throughout our lifetime.