In a major scientific development, US biologists have created cloned monkey embryos and successfully transferred them into monkey mothers. "If researchers are able to repeat this process in monkeys, it might help them to refine the tricky technique without experimenting on human eggs and embryos, which are very difficult to obtain and raise a host of ethical objections," the Nature magazine reported. "It might help solve the mystery whether human embryonic stem cells, which can grow in a variety of tissues, will prove useful in medicine."