Children begin teething around six months of age. The technical term for these early teeth is deciduous teeth, because they eventually fall out, just as leaves fall of from deciduous trees in autumn. Most people know these teeth as baby teeth, though they are also sometimes called milk teeth or primary teeth. In all, children have 20 baby teeth - 10 on the top and 10 on the bottom. These teeth act as placeholders for the adult teeth that grow in after the baby teeth fall out.