Editor's Note: In an American Morning original series, "Big Stars, Big Giving," CNN National Correspondent Alina Cho looks at celebrity philanthropy and how these big stars can make a big impact. Through one-on-one interviews with Nicole Kidman, Halle Berry, Edward Norton, Julianne Moore and Justin Bieber, she shares what causes have become their passions, and … Continue reading Big Stars, Big Giving: Justin Bieber on getting his fans involved in doing good for others