Scientists at EPFL have created a scalable 3D organoid model that captures key features of early limb development, revealing how a specialized signaling center shapes both cell identity and tissue organization.
During early development, the embryo builds the body’s organs by exchanging chemical signals between different cell types. When developing limbs, a thin band of skin cells at the limb’s surface, called the “apical ectodermal ridge” (AER), sends signals that guide the underlying population as it grows and forms bone, cartilage, and connective tissue.
The AER is hard to study because it forms only briefly in the embryo and secretes several types of signaling molecules at once. Studying these interactions in embryos is difficult, so scientists often turn to organoids, tiny lab-grown organs that offer researchers a controlled way to study how cells behave and interact as tissues form.









