Kyoto University Naïve and primed PSCs (iPS cells and embryonic stem cells) represent different periods in development (before and after the embryo implants itself into the uterus). Naïve PSCs can become all the major cell components that make up the villi, which goes on to become the placenta. Primed PSCs cannot and instead form cells that lead to the amnion. The Yasuhiro Takashima lab shows that naïve iPS cells can be induced to form all the stages that mimic early placenta development in humans. Gynecologist Shingo Io knows that during birth there will not only be a baby leaving the mother’s body. Joining the cries that bring joy to the room will be a silent entity, the placenta. Like the baby, this tissue only began to grow upon conception, but little is known about how the placenta develops inside the mother. A new study by Io, CiRA Junior Associate Professor Yasuhiro Takashima and colleagues reports how iPS cells can be used to study this development. The