Anderson CooperNow in its fourth year, CNN Heroes is a multi-platform campaign that shines a spotlight on individuals who go to extraordinary lengths to serve others. In 2010, the campaign received over 10,000 submissions from more than 100 countries and Anuradha Koirala was named the 2010 CNN Hero Of The Year. She is fighting to prevent the trafficking and sexual exploitation of Nepal's women and girls.

Renee Zellweger and Marissa Tomei were among the celebrities in attendance to help celebrate the heroes' acts of kindness, courage and perseverance.

Watch a sneak peek of 'CNN Heroes: An All-Star Tribute' hosted by Anderson Cooper, which airs Thanksgiving night (11/25) at 8PM ET on CNN.