mRNAs are expression factors that mimic fully processed mRNA. Being the substrate for translation by ribosomes, mRNA expression factors are often preferred over viral vectors for cell reprogramming and iPS cell generation because of the absent risk of integration into the genome. Such RNA-induced pluripotent stem cells (RiPSCs described in 2010 by Warren et al.) are becoming more and more popular. 3 reasons might illustrate RiPSCs’ attractivty.