Scientists grow and observe mouse embryos outside the womb Researchers kept bottled mouse embryos alive about halfway through their usual gestation, observing formation of hind limbs and major organs. A mouse embryo growing inside a beaker. Photo courtesy of Weizmann Institute Nature that information about mammalian embryonic development comes either from observing the process in non-mammals like frogs or fish that lay transparent eggs, or by obtaining static images from dissected mouse embryos. A mouse embryo grown six days outside the uterus reveals normal developmental markers. Photo courtesy of Weizmann Institute The idea of growing embryos outside the uterus has been around since before the 1930s, Hanna said, but experiments had limited success and the embryos tended to be abnormal.