The present invention relates to methods for changing the state of differentiation of a eukaryotic cell, the methods comprising introducing mRNA encoding one or more reprogramming factors into a cell and maintaining the cell under conditions wherein the cell is viable and the mRNA that is introduced into the cell is expressed in sufficient amount and for sufficient time to generate a cell that exhibits a changed state of differentiation compared to the cell into which the mRNA was introduced, and compositions therefor. For example, the present invention provides mRNA molecules and methods for their use to reprogram human somatic cells into pluripotent stem cells.