hmmm…I understand the use of the excess but the controversy is about producing and destroying it wholly for the purpose of stem cell research.
Embryonic stem cell research currently requires the fertilization of an embryo with the plan to use it as a source for collecting embryonic stem cells[SUP]citation needed][/SUP], which results in the destruction of the embryo. This deliberate creation and destruction of a human embryo is a primary source for the ethical controversy.