Scientists have created synthetic mouse embryos from stem cells without a dad’s sperm or a mom’s egg and womb. The lab-created embryos mirror natural mouse embryos up to 8 ½ days after fertilization, with structures including one like a beating heart. Research on the synthetic embryos was published Thursday in the journal Nature and is similar to research published earlier this month in the journal Cell. In the near term, researchers hope this will provide a model to do research without the need for as many lab animals. The feat could also lay the foundation for creating synthetic human embryos in the future.