Few articles in recent years have generated such interest and excitement as the report by Takahashi and Yamanaka that adult stem cells could be reprogrammed to a pluripotent state. This study, closely followed bymany others, demonstrated that cells from somatic tissue were not permanently differentiated and could, through the forced expression of specific transcription factors, be reprogrammed into cells that had all the transdifferentiation capacities of embryonic or other previously defined stem cell forms. The potential of these findings was immediately evident to not only stem cell biologists but also to scientists and physicians working in many diverse areas of medicine. The use of embryonic stem cells had already shown the enormous potential of stem cell medicine in allowing the generation of different tissues, organs, and eventually whole organisms but was still limited both technically and ethically by the reliance on embryonic tissue. Therefore the ability to take cell types, such as skin fibroblasts or, more recently, peripheral blood, and generate induced pluripotent stem (iPS) cells and then differentiate them into numerous other cell types provided a far more accessible and almost limitless mechanism to understand disease pathogenesis, screen for drug interventions, and develop regenerative or gene-modifying therapeutic strategies. In this edition of the Journal, Pessach et al demonstrate that iPS cells can be generated for various different forms of immunodeficiencies. This in itself is not entirely novel because iPS cells generated from a patient with adenosine deaminase deficiency–severe combined immunodeficiency have been previously reported, and it is very likely that iPS cells from patients with other immunodeficiencies are currently being generated inmany other laboratories. However, although this is the first formal report of this technique for a number of different forms of immunodeficiency, the importance of this article lies not in the technology or the rigor with which these lines have been characterized but in the possibilities that this technology holds for primary immunodeficiencies.