In summary, the field of iN cell reprogramming has come a long way since it first discovery just three years ago [6]. In this review we have discussed the remarkable progress that has been made regarding functional maturation and subtype specification, but we have also outlined the current limits and challenges to further improve the technology in order to be able to apply it for disease modeling. A common theme in the subtype specification of iN cells is that certain traits of neuronal subtypes that often include relevant functional properties can be induced but the cells do not adopt a complete “authentic” phenotype. While it is conceivable that further optimization of the reprogramming protocols will lead to generation of iN cells more similar to a specific authentic brain cell type, the question arises whether it will ever be possible to generate a perfectly matching cell in culture. This might be impossible even from ES or iPS cells given that the 3-dimensional context neurons usually are exposed to might provide essential clues for their final phenotype that might be very difficult
