Embryonic stem cells have never been demonstrated to cure anything; they provide temporary alleviation at best. The problem with these cells is precisely what scientists initially thought would make them so useful; they have no, for lack of a better term, assigned function. They don’t know what they’re supposed to make so, in many cases, they replicate out of control and form tumors along the spinal column and brain. Adult stem cells, which have programed functions for specific cell type replication, work.