The white arrows in these two tumor samples point to a subset of tumor cells that are in a resting state. Nature hide caption

itoggle caption Nature

While talking with the media outside the Exciting Idlewild Baptist Church in Lutz, Fla., on Sunday, former House Speaker Newt Gingrich called for a commission to look at new rules for clinics that perform in vitro fertilization. Matt Rourke/AP hide caption

itoggle caption Matt Rourke/AP

Dr. Paolo Macchiarini, of Karolinska University Hospital, implants a synthetic windpipe. Karolinska Institute hide caption

itoggle caption Karolinska Institute