Ultrastructure of collagen matrices. Scanning electron micrographs of side views of 4 layered collagen matrix (A), showing indistinguishable interface between layers, magnified image to show dense fibrillar structure 10,000× (B), and 50,000× (C). Transmission electron micrographs of 4 layered collagen matrix (D), magnified image to show dense fibrillar structure at interface of collagen layers (E), and magnified image of a showing D-periodic banding pattern (F). *Top of layered construct. Box shows interface region between two collagen layers.