The placenta—a Frisbee-size hunk of tissue that chaperones a fetus in the uterus only to be tossed aside in the delivery room—has mysterious beginnings. The organ emerges from a set of cells that develop alongside the embryo and have been difficult to grow in the lab. Now, researchers have devised a way to derive and observe early precursors of placental cells in a dish. They have found a method of “reprogramming” adult cells, reverting them to a primitive state, that can prompt them to become trophoblast stem cells, which give rise to placental cells. The method promises a new window on how defects in placental development may lead to infertility, miscarriage, and preeclampsia.