Collagen bundles. Scanning electron micrograph (SEM) of collagen bundles from the delicate connective tissue endoneurium. Endoneurium wraps around and between individual nerve fibres (axons), providing support and filling space between the nerve fibres. Endoneurium consists of collagen and elastin fibres and is found in the peripheral nervous system. The characteristic banding of collagen can be seen in this image. Magnification not known.