More recently, the IVF revolution has enabled early human embryos to be studied in unprecedented detail outside the body, but still gastrulation has remained a mystery. Technical limitations have meant that no one has been able to keep them alive much beyond nine days, about halfway to the key developmental stage when the simple ball of embryonic cells begins to take on the identity of a proper body plan, with a top and a bottom, and the first signs of the distinctive triple layer of tissues that form the disc‑shaped “gastrula”.
Inside the ‘Black Box’ of Human Development
