NIH3T3 cells were cultured on the different surfaces for 24 hours and then fixed for immunofluorescence staining. Panels A-C are cells labeled with FITC-phalloidin. Panels D-F are cells labeled with antibodies directed against FAK phosphorylated on tyrosine 397 (FAK Y397) and panels G-I are cell labeled with antibodies directed against paxillin. Preparations in Panels (A, D, G) are thin films of fibrillar collagen; (B, E, H) are thin films prepared from the lower concentration of collagen; and (C, F, I) thin films of fibronectin. Arrows in E, F and arrowheads in G, H identify FAK Y397 staining and paxillin staining localized in focal adhesion-like plaques respectively. Microscopy images were taken using a 40× objective and the calibration bar equals 10 μm.