Scientists have devised two new techniques designed to alleviate ethical concerns. In one, the cells are derived without the need to destroy an embryo, the principal objection of anti-abortion advocates who have strenuously opposed federal financing of the research. The other technique makes a skin cell revert to the embryonic state in a way that prevents the embryo from implanting in the uterus. Both techniques, described in the online edition of Nature, have been developed in mice and have yet to be adapted to people, but the two species are very similar at this level of embryonic development.