Stem cell research requires the fertilising of sperm and egg cells followed by scientists taking stem cells out to study them. Only an embryo of less than 80 cells is useful to scientists because past 80, the stem cells have decided what they will become. Before the embryo becomes a clump of 80 cells, the stem cells can become any kind of body cell. To some religions, like Christianity, fertilisation is when life begins and they are against the taking of stem cells because they say it’s got the potential to be a fetus. However, most stem cell reasearch is in a lab under slides from donated sperm and egg cells. This process barely ever takes place in the woman’s body, so scientists believe it is ok to take stem cells from it, considering the cells were donated