Cells simultaneously assemble and maintain different actin cytoskeleton networks of distinct organizations and dynamics for fundamental processes such as polarization, endocytosis, motility and division. How does a shared pool of actin monomer building blocks self-organize into distinct actin filament networks of specific densities, sizes and function within a common cellular cytoplasm? Our research group is investigating the molecular mechanisms that govern how diverse actin cytoskeleton networks self-organize through (1) competition for a limited supply of actin monomers, (2) network-specific sorting of actin binding proteins, and (3) the effects of different combinations of actin binding proteins on actin filament network organization, dynamics and function. We take advantage of complementary experiments in live cells and with purified components. These interdisciplinary techniques include genetics, time-lapse fluorescence microscopy of cells, biochemistry, biophysics, in vitro reconstitution and multi-color single molecule TIRF microscopy imaging.