A 3D-model of a bone cell (osteocyte; pink) within cortical bone. The cell body (round) has a network of extensions (canaliculi) protruding out from it, that interconnect with other cells in the bone. Cortical bone is dense, compact bone which forms the outer shell of most bones. This image was created by reconstructing serial sections through a piece of bone, which were imaged by scanning electron microscopy. Width of image is 25 micrometres.