Embryonic stem cells (ESCs) are the most well-known type of pluripotent stem cell, however the generation of ESCs from human embryos has resulted in a great deal of controversy surrounding their use. A major breakthrough in the ﬁeld of regenerative medicine came with the introduction of induced pluripotent stem cells (iPSCs), which are a type of pluripotent stem cell generated directly from adult cells. IPCSs offer an unlimited supply of autologous cells that could be used without the risk of immune rejection.
In order to use ESCs and iPSCs for therapeutic purposes or as research tools, they must be differentiated in-vitro into fully-functioning, specialized cells. The desired differentiation is accomplished by exposing the cells to speciﬁc chemical and physical signals. The chemical signals include cytokines, growth factors, and small molecules, which activate or inhibit speciﬁc cellular pathways in order to achieve a chosen cell fate.