Current Forbes cover subject, 41-year-old Sara Blakley is the youngest woman ever to make the magazine’s annual list of billionaires without the aid of an inheritance or her husband.

She owes her wealth all to Spanx, the slimming undergarment she invented after she was frustrated by the way her backside looked in a pair of white pants. Instead of wearing the thick body-shapers available at the time, she cut off the feet of some control-top pantyhose and Spanx were born.

Blakely’s invention has become popular largely based on word of mouth, especially after such stars as Gwyneth Paltrow and Oprah Winfrey let it slip that they wore Spanx to help keep their figures in line. Blakely explained, “It’s the power of the brand. We’ve never formally advertised.”