Human embryo replicas have gotten more complex. Here’s what you need to know
The lab-engineered models give scientists a look at human development beyond the first week
A 6-day-old embryo model from Jacob Hanna’s lab in Israel has structures akin to ones found in human embryos 12 days after fertilization. Those structures include a ball of cells (top, purple) that resemble the layer that forms the body, and a hollow circle of cells (bottom, blue) mimicking the yolk sac, all surrounded by a layer of cells similar to a placenta-forming layer in human embryos.