Margaret Gardel and David Kovar from the University of Chicago MRSECare working to understand how the structure and mechanics of biopolymer networks of F-actin, a mechanical scaffold of living cells, are controlled. They have recently demonstrated that the architecture of these networks is governed by the kinetics of polymer assembly . As illustrated above, when the density of nucleates is increased, the density of bundles formed changes non-monotonically despite a constant chemical composition. A myriad of regulatory proteins found in cells regulate nucleation and elongation rates. This work sheds light as to how biopolymer networks found within cells and the extracellular matrix are regulated and provides insight into mechanisms for reconstituting these processes in artificial cells and tissues.