Marielle Heller on her film "The Diary of a Teenage Girl," which premieres in the U.S. Dramatic Competition at the 2015 Sundance Film Festival. Learn more about "The Diary of a Teenage Girl" at: http://www.sundance.org/projects/the-diary-of-a-teenage-girl-2a322f13-86f6-4054-bca5-398ed0718317 The Official YouTube Channel of the Sundance Film Festival, presented by the non-profit Sundance Institute. Enjoy up-to-the minute coverage of the Festival, including filmmaker panels, interviews and behind-the-scenes footage.