Cell-permeable. A selective inhibitor of non-muscle myosin II ATPases. It rapidly and reversibly inhibits Mg-ATPase activity and in vitro motility of non-muscle myosin IIA and IIB for several species (IC₅₀ = 0.5-5.0 μM), while weakly inhibiting smooth muscle myosin (IC₅₀ = 80 μM). Through these effects, blebbistatin reversibly blocks apoptosis-related bleb formation, directed cell migration and cytokinesis in vertebrate cells.