Actin Nucleation By ARP-WASP Complex For many cell types, the ability to move across a solid surface is fundamental to their biological function. Certain aspects of cell locomotion, such as the protrusion of the plasma membrane in lamellipodia and filopodia, are driven by the polymerization of actin cytoskeleton. The actin cytoskeleton is a dynamic filament network that is essential for cell movement during embryo development, polarization, morphogenesis, cell division, and immune system function and in the metastasis of cancer cells. To engage in these complex behaviors, cells must direct actin assembly with a high degree of spatial and temporal resolution in response to extracellular signals (Ref.1). To coordinate these behaviors, tight spatial and temporal control is exerted over several aspects [...]