“If human embryonic stem cell research does not make you at least a little bit uncomfortable, you have not thought about it enough,” he said. “I thought long and hard about whether I would do it.”

He decided in the end to go ahead, reasoning that the work was important and that he was using embryos from fertility clinics that would have been destroyed otherwise. The couples whose sperm and eggs were used to create the embryos had said they no longer wanted them. Nonetheless, Dr. Thomson said, announcing that he had obtained human embryonic stem cells was “scary,” adding, “It was not known how it would be received.”

But he never anticipated the extent and rancor of the stem cell debate. For nearly a decade now, the issue has bitterly divided patients and politicians, religious groups and researchers.

Now with the new technique, which involves adding just four genes to ordinary adult skin cells, it will not be long, he says, before the stem cell wars are a distant memory. “A decade from now, this will be just a funny historical footnote,” Dr. Thomson said in the interview.

As for the science behind it, the thrill of discovery, he said, “Surprisingly, there is no ‘Wow’ moment,” either from 1998 or now. Both times, the discovery came after he had spent months rigorously testing the cells to be sure they really were stem cells, worrying all the while that they could die or be lost to contamination. When he knew he had succeeded, the suspense was gone.