Stem cells have revolutionised the field of biological research. The holy grail of the stem cell research have been embryonic stem cells whose harvesting and exploitation is drowned in controversy because of their origin. A well-known fact is that these cells are totipotent, i.e. capable of differentiating into virtually any other cell type. However, programmed for fast growth, they bear a high risk of tumor formation post-transplantation (Nussbaum et al., 2007; Wakitani et al., 2003) and are subject to potential rejection by the host recipient.