Scientists at Advanced Cell Technology announced yesterday that they’ve derived colonies of stem cells from human embryos without doing any damage to those original embryos. The work is significant because it may meet the ethical guidelines of the Bush Administration, which insist that no harm be done to the embryos in pursuing this brand of stem cell research. At the same time, it might not be that clear cut, since the definition of “harm” is a bit tricky in this space, as this Washington Post article points out. The work differs from this past summer‘s big advance, in which scientists dodged the ethical issue altogether, and derived embyonic stem cells from mature cells.—Gregory Mone