Development leads unidirectionally towards a more restricted cell fate that is usually stable. However, it has been proven that developmental systems are reversible by the success of animal cloning of a differentiated somatic genome through somatic cell nuclear transfer (SCNT). Recently, reprogramming of somatic cells to a pluripotent embryonic stem cell (ESC)-like state by introducing defined transcripton factor has been achieved, resulting in the generation of induced pluripotent stem cells (iPSCs), which resemble ESCs. iPSC reprogramming is of great medical interest, as it has the potential to generate a source of patient-specific cells. However, the dangerous delivery method, low efficiency, and slow kinetics of the reprogramming process have hampered progress with this technology.