The nucleation of actin filaments by the Arp2/3 complex, which can be activated by Scar/WAVE, is essential for many eukaryotic cellular processes,including cell migration in animals and plant epidermal cell morphogenesis. Genetic studies in Arabidopsis have revealed the functions of several conserved components of a Scar/WAVE regulatory complex during trichome(epidermal hair) formation. Now, Djakovic and colleagues report that BRICK1(BRK1), the plant homolog of the mammalian Scar/WAVE complex component HSPC300, regulates epidermal cell shape in Arabidopsis in concert with SCAR and the ARP2/3 complex (see p. 1091). The researchers show that mutations in BRK1 cause similar morphological defects in trichomes and other epidermal cells to those caused by mutations that disrupt the ARP2/3 complex. Epidermal defects in plants containing mutations in both BRK1 and ARP2/3 components are no more extreme than those in single mutants,indicating that BRK1 acts within the ARP2/3 pathway. Finally, the researchers show that BRK1 protects SCAR1 protein from degradation, which may explain how BRK1 controls ARP2/3 complex activity.