Inhibition of myosin II activity constrains traction to the lamellipodium. (A–C) Cells were treated with 50 μM blebbistatin (+BLEB). (A) Heat scale plot of traction stress magnitude. (B) Mean traction stress (green) and F-actin speed (blue) as a function of distance from leading cell edge. (C) Immunofluorescence image of paxillin (red) and F-actin (green). Bars, 5 μm.