Editor's Note: In an American Morning original series, “Big Stars, Big Giving,” Alina Cho looks at celebrity philanthropy and how these big stars can make a big impact. Through one-on-one interviews with Elton John, Ben Stiller, Madonna, Martha Stewart and Richard Branson, she shares what causes have become their passion, and how you can get involved. In part five, Alina sits down with Virgin mogul Richard Branson. Friday, 6-9 a.m. ET – only on CNN.

In part four of the American Morning original series, "Big Stars, Big Giving," Alina Cho interviews Martha Stewart about her Center for the Living, where the elderly can age gracefully.

To learn more about the organizations these stars have created to make a difference,

and how you can get involved, visit Impact Your World.