Single-cell gene expression analyses of cellular reprogramming reveal a stochastic early and hierarchic late phase 5 d9 K/ O1 k2 \8 H" ?$ QYosef Buganim , Dina A. Faddah , Albert W. Cheng , Elena Itskovich , Styliani Markoulaki , Kibibi Ganz , Sandy L. Klemm , Alexander van Oudenaarden , and Rudolf Jaenisch