Researchers have uncovered the balance of physical forces that embryos use to shape themselves — and it looks a lot like what happens in materials like glass or foam.https://www.quantamagazine.org/traffic-jams-of-cells-help-to-sculpt-embryos-20180927/ …
I bet this fluid-transition theory applies to stem cell differentiation in vitro. I've worked with making cardiac cells - ineffective differentiations sometimes get stuck in a "popped-bubble" shape.