Human embryo development and early organ formation remain largely unexplored due to ethical issues surrounding the use of embryos for research as well as limited availability of materials to study. In a paper published April 6 in the journal Cell Stem Cell, a team of investigators from China report for the first time the creation of embryo-like structures from monkey embryonic stem cells. The investigators also transferred these embryo-like structures into the uteruses of female monkeys and determined that the structures were able to implant and elicit a hormonal response similar to pregnancy.