This assay represents a simplified model of muscle force and motion generation.  In this assay, myosin, a molecular motor, is adhered to a nitrocellulose-coated microscope coverslip. The coverslip is one surface of a 20 µl experimental microchamber. Fluorescently labeled actin filaments in a solution containing MgATP are perfused into the chamber and then the movement of single actin filaments over the myosin surface is visualized in a Total Internal Reflectance Fluorescence (TIRF) microscope. Variations of this assay include the use of native myosin thick filaments and native actin thin filaments.