Odontogenesis is a complex process regulated by both genetic and molecular controls. The development of a tooth in the embryo stage is controlled by a series of signals which occur between tooth-forming epithelium and neural crest-derived ectomesenchyme. Though many genes are involved in tooth formation involving major signalling molecules, the bone morphogenetic protein and fibroblast growth factor are the most important ones involved in odontogenesis. Supernumerary tooth occurs because of imbalance in the expression of the signalling pathways and their inhibitors. This review highlights the various signalling molecules that play a role in odontogenesis in order to provide a better understanding on of the molecular mechanisms involved in the formation of supernumerary tooth in humans.