 The choice of the sub-periosteum site is used because stimulation of the cambium layer using transforming growth factor–beta resulted in enhanced chondrogenesis, i.e., formation of cartilage.In development the formation of bone can either occur via a Cartilage template initially formed by the MSCs that then gets ossified through a process called endochondral ossification or directly from MSC differentiation to bone via a process termed "intra-membranous ossification".Upon exposure of the periosteal cells to calcium from the alginate gel, these cells become bone cells and start producing bone matrix through the intra-membranous ossification process, recapitulating all steps of bone matrix deposition.