Pluripotent stem cells can develop into most tissues of the organism, but they cannot develop into extra-embryonic tissue — the placenta or yolk sac, for example — like the one-celled fertilized egg or two-celled zygote. Researchers found that by blocking a specific microRNA, pluripotent stem cells can regain the ability to become extra-embryonic tissue, providing a way to expand the developmental potential of iPC cells with implications for regenerative medicine and stem cell-based therapies.