Tooth dentine-pulp boundary. Coloured scanning electron micrograph (SEM) of the boundary between the yellow dentine (substantia eburnea), which is a mineralised connective tissue found under a tooth's enamel, and the pulp (not seen). The pulp, the soft tissue containing nerves and blood vessels that makes up the inner part of the tooth, has been removed to reveal the dentinal tubules (dental canaliculi). These tubules are minute holes in the dentine that have been formed by the cytoplasmic extensions (pink) of odontoblast cells (dentine-producing cells). The odontoblast cells originate in the pulp and allow the dentine to rebuild itself, unlike enamel. Magnification: x830 when printed 10 centimetres wide.