What is stem cell research controversy all about? cant it help?

Stemcell controversy: All humans first start as a fertilized ovum, which is totipotent ("potential to become every cell"). After several days, it grows into an embryo, comprised of embryonic stem cells. Embryonic stem cells are described as being pluripotent ("potential to become a wide variety of cells"). The main controversy has to do with the use of human cells, abortions, and the ethics of using these cells.