Light microscopy of attachment of periosteum to spongy bone. Strong bundles of collagen (Sharpey?檚 fibres) anchor the tissues covering the bone surface to the deeper lattice-shaped profiles of bone. Regions between the bone are filled with yellow or fatty-type bone marrow. Sharpey?檚 fibres are particularly important for anchoring teeth into their bony sockets. Magnification x 90 when printed at 10 cm.