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 cells that develop alongside the embryo, and that 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 (TSCs), which give rise to placental cells.