The new field of epigenetics sees that genes can be turned on and off and expressed differently through changes in environment and behavior. Rachel Yehuda is a pioneer in understanding how the effects of stress and trauma can transmit biologically, beyond cataclysmic events, to the next generation. She has studied the children of Holocaust survivors and of pregnant women who survived the 9/11 attacks. But her science is a form of power for flourishing beyond the traumas large and small that mark each of our lives and those of our families and communities.