A subpopulation of filopodia are involved in the initiation of substrate adhesion. (A) Two video frames of a CAR fibroblast expressing mCherry-actin and EGFP-paxillin separated by 21 min and showing (marked on the right with arrowheads) those adhesion sites whose origin could be traced to a position along a filopodium. (B and C) Video frames of selected regions taken from the cell in A showing the appearance of focal complexes along filopodia (arrowheads; see Video 9). Small arrows in C indicate development of filopodia into bundles in the lamella, with focal adhesions at their ends. (D) Video frames of a cell transfected as in A and showing the bending of filopodia (marked 1–3) around adhesion foci (arrowheads). Times are given in minutes and seconds. Bars: (A) 10 μm; (B–D) 5 μm.