Distinct roles of actin architecture and tension in focal adhesion maturation. (1) Nascent adhesions under low tension (0–0.3 nN) assemble in the lamellipodia and turnover on minute time scales. (2) A small amount of tension (∼1 nN) generated by myosin II in the lamella stabilizes the adhesions to the ECM. Accumulation of F-actin at the adhesion occurs via an RSF template mediated by Dia1-driven polymerization of F-actin and stabilized by α-actinin cross-linking. (3) The RSF template promotes recruitment of focal adhesion (FA) proteins to facilitate compositional changes. (4) Lamellar retrograde flow drives elongation of the RSF template into an elongated stress fiber as well as adhesion growth. The maturation process that ultimately results in fibrillogenesis can occur over a large range of myosin-generated stresses but is quite sensitive to the actin density at the adhesion plaque. Alternately, compositionally immature adhesions (2) are sufficient to transmit large traction stresses to the ECM, with the stress magnitude dependent on the nature of force transmission in the actin cytoskeleton rather than the size or composition of the adhesion plaque.