(S)-Blebbistatin is a cell-permeable, potent, and selective inhibitor of non-muscle myosin II (NMM II) ATPase activity. It is the active enantiomer of the racemic mixture, exhibiting significantly higher potency. The compound specifically targets the ATPase activity of myosin II, effectively blocking its interaction with actin filaments, which is crucial for cellular processes such as cytokinesis, cell migration, and maintenance of cell shape. Its primary application is as a highly valuable research tool in cell biology and developmental biology. (S)-Blebbistatin is extensively used in vitro to study the role of myosin II in various cellular functions, including cell division, adhesion, and motility. It has become a standard reagent for inhibiting actomyosin contractility to investigate mechanisms underlying processes like embryonic development, wound healing, and cancer cell invasion. Furthermore, due to its role in modulating cellular tension and morphology, it has shown research potential in areas related to cardiovascular diseases and skeletal muscle disorders. While primarily a research chemical, studies have explored its therapeutic potential. For instance, its ability to reduce cellular contractility has been investigated in contexts such as preventing hypertrophic scar formation, mitigating ischemia-reperfusion injury in the heart, and as a potential agent for diseases involving excessive cellular contraction. It is typically used in the low micromolar range (1-10 µM) in cell culture experiments. As a light-sensitive compound, it requires handling and storage protected from light to maintain stability.