Fig. 2. The adhesion lifetime. Adhesions first form in the lamellipodium, where their rate of assembly correlates with the rate of protrusion. As actin disassembles at the rear of the lamellipodium, adhesions turn over. Some adhesions elongate in the region of convergence between the lamellipodium and the lamellum, and mature centripetally along thin actin filaments that are decorated with -actinin, an actin cross-linker (depicted in red). As the bundles become thicker and more stable owing to enhanced cross-linking, myosin II (depicted in green) enters and the adhesions become larger.