Schematic illustration of the different fates of filopodia. Large arrow indicates direction of movement. (1 and 1′) Filopodia fold laterally in opposite directions into the cell edge, forming a bundle with antiparallel filaments that integrates into the lamella as the cell edge advances. Integration is coupled with the incorporation of myosin and actin cross-linkers into the bundle. Single filaments originating from the lamellipodium can also contribute to these bundles. (2) A few filopodia kink as a result of lamellipodial retrograde flow and can release fragments into the lamella. (3 and 3′). An early adhesion (focal complex) forms underneath a filopodium. The part of the filopodium distal to the adhesion retracts or folds away, finally separating from the point of adhesion. The proximal part of the filopodium links with oppositely polarized filaments in the lamella via interaction with myosin and actin cross-linkers, forming a contractile stress fiber and resulting in the maturation of the focal complex into a focal adhesion. Again, filaments originating from the lamellipodium can potentially be recruited into the bundle. (4 and 4′). A filopodium folds up and back into the lamella.