Coloured scanning electron micrograph (SEM) of a freeze-fracture through the jaw of a 16.5 day old mouse embryo showing the cells involved in tooth development. The red cells are pre-ameloblasts and the yellow cells are pre-odontoblasts. Ameloblasts are the cells that secrete the enamel that covers the crown (visible part) of the tooth. Odontoblasts create dentine, the mineralised connective tissue that forms the bulk of the tooth. The picture was created as part of a cooperation with Quintessenz Publishing. Magnification: x2,500 when printed at 15cm wide.