The human embryonic stem cell, which could be used to grow any other human tissue, has been a stubborn and elusive prey (see "The Troubled Hunt for the Ultimate Cell," TR July/August 1998). Now, in the scientific equivalent of a photo finish, two teams have announced, in Science and Proceedings of the National Academy of Sciences, respectively, the isolation of stem cells from human embryos. Their results could have very significant implications for biological research and transplant medicine.

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