They're smart, sexy, feisty, athletic, and confident. They're nothing like any generation that's gone before. And if you think they're formidable now, says Amanda Robb, wait till they get out of school.

Alpha girls. Phat girls. Riot grrrls. Girly gurls. Divas. Jockettes. Suddenly they're swaggering everywhere, showing off curves that pop out of their hip-huggers. Dribbling basketballs with their meticulously manicured hands. Rolling their eyes at boys' catcalls and charging into an astonishing future. As my friends and I make way for them on sidewalks and ready ourselves for the rapidly approaching day they bound into our offices, we have one question: Where did they come from?

This winter I went on a fact-finding mission around the country to learn what's fueling this explosion of girlhood achievement and what it feels like to be growing up in the midst of a cultural blast ring. I interviewed more than a hundred girls, from ages 8 to 22—girls who are passionate about knitting, fractal geometry, green garbage, and their friends. Even before we started talking, they had me amazed.