Erika Christakis, M.P.H, M.Ed., is an early childhood educator at the Yale Child Study Center. Follow her on Twitter @ErikaChristakis.
Nicholas A. Christakis, M.D., Ph.D., is the co-director of the Institute of Network Science at Yale University. Nicholas was named to the TIME 100 in 2009. Follow him on Twitter @NAChristakis.