Osteoblasts. Coloured transmission electron micrograph of osteoblasts, bone-producing cells (pink). They contain rough endoplasmic reticulum (RER, dark pink lines), which produces, modifies and transports proteins, and a nucleus (purple), which contains the cell's genetic information. Mitochondria (oval, dark pink) provide the cell with energy. The cells produce the collagen, or osteoid, that provides the framework for the mineralised matrix of bone (green, upper right). Magnification: x2600 when printed 10 centimetres wide.