Fig. 1From: Modelling in vitro gametogenesis using induced pluripotent stem cells: a reviewKey methods for introducing reprogramming factors. Whereas integrating viral systems (1) were the first to be used, it incorporated viral genetic material that caused teratoma. Newer methods (2–4) avoid this and significantly improves the safety and efficacy of iPSCs especially for clinical applications. (Modified from Liu et al. 2020)Back to article page