Protrusion of the leading edge represents the first step of cell migration. This process is connected with formation of cytoskeletal actin-containing structures called lamellipodia and filopodia. Reorganization of cortical actin filaments in response to extracellular stimuli is controlled by The Wiskott- Aldrich syndrome proteins (WASP), a protein family members that are believed to be important effectors of Rho GTPases and to mediate in activating Arp2/3 (actin-related protein 2-3) complex. Recent studies using quantitative fluorescent speckle microscopy (qFSM) revealed the existence of the second region containing filamentous actin at the leading edge of migrating cells – lamellum, responsible for the persistent advancement of the cell. In this paper, characteristics of above-mentioned structures are presented and the mechanisms and signaling pathways leading to their formation, are discussed.