Osteoblast. Coloured scanning electron micrograph of a bone-making osteoblast cell surrounded by a dense network of collagen fibres. The numerous filipodia on the cell surface project into the surrounding matrix and maintain contact with other osteoblasts. Osteoblasts produce the organic matrix of bone, a substance called osteoid. This consists of a mass of collagen fibres and a glycoprotein cement. As soon as osteoid is formed, calcium salts crystallise inside it to form hard, mineralised bone. Osteoblasts that become trapped in cavities in the bone become osteocytes. Magnification: x2200 at 5x7cm size. Magnification x1100 at 35mm size.