Cancellous bone. Light micrograph of a section through cancellous (spongy) bone from the humerus (upper arm bone). Cancellous bone is found in a bone's interior. It is characterised by a honeycomb arrangement, comprising a network of trabeculae (red) fibrous tissue. The trabeculae are composed of irregular lamellae of bone and lacunae (cavities) containing osteocytes (purple). Osteocytes are osteoblasts (bone-producing cells) that have become trapped in lacunae. These structures provide support and strength to the bone. The spaces within this tissue contain bone marrow (light purple), a blood forming substance.