Best friends Mia Koniver, 32, and Lizzie Scheck, 31, were looking for a hobby when they started crafting jewelry in 1998. "We were just playing," Scheck recalls of the duo's early efforts at stringing semiprecious stones. "But then friends and store owners started saying, 'I want that'—and the next thing I knew, we were in business."

Today Mia & Lizzie jewelry, priced from $400 (gold pinky rings) to $6,000 (a diamond bow-tie pendant necklace) and sold nationwide at stores like Neiman Marcus and Bergdorf Goodman, is captivating celebs too. Sarah Jessica Parker chose a large diamond horseshoe necklace ($2,200) as her signature Sex and the City piece last season, creating a run on the item (it's still on about a five-month back order), while Jennifer Lopez purchased a custom-made diamond cuff earlier this year. "Mia and Lizzie," says Jennifer Kaufman, who sells the line at the hip Los Angeles boutique bearing her name, "know what a fashionable woman wants to wear."

Koniver, an actress who grew up in Wilmington, Del., and Scheck, a television casting director raised in Manhattan, know what they want too: more free time. "I'm dying to have kids," says Scheck. Luckily Mia & Lizzie's success (it's now a seven-figure business) has allowed the single business partners—who both live in L.A.—to quit their day jobs. "We've given up our social lives for three years," Koniver says. "But now I see dinner happening again."