Scientists have grown an entity that closely resembles an early human embryo, without using sperm, eggs or a womb. The Weizmann Institute team say their "embryo model", made using stem cells, looks like a textbook example of a real 14-day-old embryo. It even released hormones that turned a pregnancy test positive in the lab. (snip) Instead of a sperm and egg, the starting material was naive stem cells which were reprogrammed to gain the potential to become any type of tissue in the body. (snip) "Some will welcome this - but others won't like it," Prof Lovell-Badge says.