[www.npr.org]

"Scientists say they have, for the first time, cloned human embryos capable of producing embryonic stem cells.

The accomplishment is a long-sought step toward harnessing the potential power of embryonic stem cells to treat many human diseases. But the work also raises a host of ethical concerns.

"This is a huge scientific advance," said , a Harvard stem cell scientist who wasn't involved in the work. "But it's going to, I think, raise the specter of controversy again."

The controversy arises from several factors. The experiments involve creating and then destroying human embryos for research purposes, which some find morally repugnant. The scientists also used cloning techniques, which raise concerns that the research could lead to the cloning of people.

Ever since human embryonic stem cells were discovered, scientists have had high hopes for them because the cells can morph into any kind of cell in the body. That ability means, in theory, that they could be used eventually to treat all sorts of illnesses, including diabetes, Alzheimer's, Parkinson's and spinal cord injuries.

So for years, scientists have been trying to use cloning techniques to make embryonic stem cells that are essentially a genetic match for patients. The idea is that such a close match would prevent their bodies from rejecting the cells.

"It's been a holy grail that we've been after for years," says , a stem cell pioneer at the University of Pennsylvania.

But every previous attempt ended in failure or fraud, leading many scientists to wonder if the goal might be impossible to reach."