Fig 1: Schematic of molecular interplay during de novo microstructure organization. Secreted basement membrane proteins are directionally secreted and organized by hS/PCs at the periphery of the growing microstructure. The initial growth and coordinated movement during this maturation phase depends on ß1 integrin activation by hS/PC-secreted ligands: laminin, collagen IV, and perlecan/HSPG2. Adhesive interactions between integrins on cells and matrix or hydrogel networks surrounding them can generate traction forces large enough to drive coordinated revolutions of entire multicellular structures.