Bone tissue, light micrograph. Unstained ground section of mature bone showing osteons (Haversian systems) in cross-section composed of bone matrix and osteocytes with a central vascular (Haversian) canal. Osteons are cylindrical often 3-5cm in length, 200-250 micrometres maximum diameter with connecting branches and others ending blindly. Osteocytes extend many cytoplasmic processes into the bone matrix and serve for exchange of nutrients (such as calcium or phosphate) between the matrix and the living osteocytes. Magnification: x100 when width printed at 10cm.