Yue Shao had never seen anything quite like it.
Two years ago, Shao, a mechanical engineer with a flair for biology, was working with embryonic stem cells, the kind derived from human embryos able to form any cell type. As he experimented with ways of getting cells to form more organized three-dimensional structures by growing them in scaffolds of soft gel, he was looking for signs of primitive neural tissue.
What drew his attention was that the cells seemed to change much faster than expected—they arranged themselves rapidly over a few days into a lopsided circle.
What was it? Shao startled Googling to see if he could identify the structure. That’s when he landed on a website called The Virtual Human Embryo and found some microscope photos of ten-day old human embryos shortly after implantation, fused to the uterine wall. There was the beginning of the amniotic sac and, inside it, the embryonic disc, or future body. They matched what he was seeing.