This technique allows one to measure the average isometric force generation of a small population of myosin molecules (<100) on the surface of the in vitro motility assay. Ultracompliant glass microneedles (0.2 mm dia., 0.5 mm length) are fabricated and their stiffness determined (2-20 pN/mm). The ends of the microneedle are coated with NEM-modified myosin that acts as super glue to attach a single actin filament to its end. Once an actin filament is attached, the microneedle is lowered to the motility surface and the actin filament allowed to interact with the myosin on the coverslip surface. As myosin pulls on the actin filament, the amount that the microneedle bends is recorded and used as a measure of force (VanBuren et al., 1992).