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*Embryonic stem cells* typically are derived from 4- to 5-day old human embryos formed via in vitro fertilization or cloning in a lab. Since embryonic stem cells are naturally “pluripotent” — able to transform themselves into any cell in the body — researchers have regarded them as the most useful. The use of embryonic stem cells has been condemned by the Catholic Church because embryos must be destroyed in the process of acquiring them.