The 2010 TIME 100

Serena Williams is one of those rare champions who have transcended sports and impacted our society. In tennis, she is as focused as she has ever been at any point in her career, and it shows. (She recently picked up her 12th Grand Slam title, the same number I won.)

But in addition to the people who follow her on the court, she has a growing legion of fans outside the sport. Serena, 28, is committed to making a difference in the lives of others. Her work with children in Kenya and here in the U.S. stresses the importance of education.

Through her charitable efforts, people are seeing her in a larger context. She has several interests — yes, tennis is one of them — but it is this new combination of success on the court and stability in her life that is creating new opportunities, for her and the people whose lives she touches.

King, a tennis champ and social-justice pioneer, is a co-founder of World Team Tennis and the founder of the Women's Sports Foundation

TIME 100 Social-Networking Index: 1,681,207