Nearly fifty years ago, it was hypothesised that terminally differentiated cells such as fibroblasts could be forced to take on a pluripotent state, similar to the embryonic stem cells (ES cells). The basis of the concept is the observation that all cell types, with minor exceptions, have the same genetic code. The only difference is how the code is read. This ability of differentiated cells to acquire a pluripotent state or, more generally, the process of cell fate conversion is termed cellular reprogramming. Reprogramming here means transition between cell fates or dedifferentiation. The classic and earliest change of direction of cell differentiation comes from the research of nuclear transfer. Another milestone showing that the nuclear transfer technology can reverse the cell fate of somatic cells to pluripotent stem cells was the production of the normal adult sheep Dolly. Recent and spectacular advances in this field fell in 2006 when mouse fibroblasts were reprogrammed to induced pluripotent stem (iPS) cells. The next big step was the in vivo reprogramming of adult pancreatic exocrine cells to beta cells. This series of excellent work turns back the clock of somatic cells to create the first (iPS) cells, or stem cells, made without the use of embryos. In this article, we will focus on cellular reprogramming; in particular on transcription factor induced reprogramming as well as its implications for therapeutic use.