Epithelial Mesenchymal Interactions play an important role in the development of various tissues such as in Odnotogenesis, Salivary gland development, Tumor formation and metastasis. Cells are comprised of epithelia and mesenchyme. The signalling which takes place between the epithelial cells and mesenchymal cells is known as Epithelial Mesenchymal Interactions. This signalling can be Unidirectional or Bi-directional.