Nicholas D. Kristof is a New York Times op-ed columnist and two-time Pulitzer Prize winner. With his wife, Sheryl WuDunn, he has written four best-selling books, including the No. 1 New York Times best-seller "Half the Sky." Kristof and WuDunn were the first married couple to win a Pulitzer for journalism, for their coverage of the Tiananmen Square democracy movement in China and the massacre that followed. Kristof later won a second for his columns from Darfur. Kristof and WuDunn live in the New York area with their three children. Kristof is active on social media, particularly Facebook (www.facebook.com/kristof) and Twitter (www.twitter.com/nickkristof). He was the first blogger on the New York Times website and the first to make a video for the site; he now has more Twitter followers than any other print journalist.