GIRLS INCORPORATED

Girls Incorporated

They are to tweens what Martha Stewart is to American homemakers: arbiters of all that is right and good and stylish. But Mary-Kate (far right) and Ashley Olsen, 15-year-old twins from San Fernando Valley, are also budding tycoons, blithely ensconced atop a cross-platform fashion-and-entertainment empire. Having infiltrated every medium known to girls aged 6 to 14, the Mary-Kate-and-Ashley brand is poised to generate $ 1 billion in revenue in 2002. The twins'clothing-and-accessories line, purveyed exclusively through Wal-Mart, is on pace to eclipse Kmart's...