Osteoblasts. Coloured transmission electron micrograph of osteoblasts, bone-producing cells (pink). They contain rough endoplasmic reticulum (RER), which produces, modifies and transports proteins, and a nucleus (purple), which contains the cell's genetic information. Mitochondria provide the cell with energy. The cells produce the collagen, or osteoid, that provides the framework for the mineralised matrix of bone (brown). Three capillaries containing red blood cells are also present. Magnification: x1000 when printed 10 centimetres wide.