Recent studies suggest these cells may hold the secret to treatment, even cures for some of our most inexplicable diseases, including Alzheimer's and Parkinson's.

Embryonic stem cells are controversial. They come from the inner cell mass of a blastocyst (term for a fertilized egg). At the heart of the stem cell debate is a battle - over abortion as, these are cells from embryos. According to the religious orthodoxy, an embryo is life. But these cells also hold great promise for millions of ailing patients and their families. Moreover, many of the embryos would otherwise be unceremoniously discarded.

Until very recently, the vast majority of stem cells used in research came from discarded (or excess) embryos stored at in-vitro fertilization clinics. If potential parents decide against having more children, scientists working with stem cells might ask them to consider donating the unneeded embryos to research.

Adult stem cells taken from the blood or organs of healthy adults have recently demonstrated an unexpected adaptability in lab experiments. But these cells are marginally helpful to scientists, and do not show the same promise as those culled from embryos. Adult cells are fairly set in their ways, and don't seem to grow or replicate themselves as quickly as their younger counterparts.

New techniques for gathering the cells are in quiet development; scientists are generally wary of disclosure, because public reaction is difficult to predict. Revelations that scientists at a privately-funded fertility clinic are growing human embryos with the intent of harvesting stem cells have provoked widespread hand-wringing, among both advocates and opponents of stem cell research. Advocates worry that publicizing such a blatant and systematic cell harvesting procedure can only harden hearts against the science; in the crude terms of public relations, using stem cells from discarded embryos is one thing, but purposefully creating an embryo only to dismantle it is something else altogether. Opponents of the research see the clinic's methodology as the best indication yet that we are carelessly sliding down the slippery slope of destroying human life in order to advance our scientific curiosity.

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