Pretty cool that they were able to get these to grow to 1.5 cm without collapsing. It's also interesting to note that a lot of the early regulatory factors involved in amnion formation (BMP signaling targets, specifically) overlap with primordial germ cell regulators. In fact germ cells can be co-specified with amnion in another stem cell system (https://pubmed.ncbi.nlm.nih.gov/37426764/)