The popularity of designer doughnuts is exploding like jelly bursting from a sugary bun. But how did these simple rings of fattening joy become so, well, cool? Stephanie Rosenbaum, San Francisco blogger and author of "World of Doughnuts" (, offers this explanation:

"Whether you live in a big city or a small town, the corner doughnut shop is always a happy place. It smells like fried food, sugar and coffee and the doughnuts are usually pretty cheap, which makes it a great equalizer -- anyone, for the price of a doughnut and a cup of coffee, can hang out there.

"You can bring a box of doughnuts to work to get everyone through yet another boring meeting, or you can hit an all-night doughnut place for a maple-bar sugar high at 3 a.m. after a night of clubbing or partying with your friends.

"I can remember the very first night I moved to San Francisco, right after college. I'd just moved into a shared apartment at 18th and Castro. I went out to the Happy Donuts shop that used to be right around there, and I got a cup of coffee and a chocolate-iced cake doughnut, and I sat on my front steps and ate my doughnut watching the parade of street life go by, and I felt like my real adult life was finally starting, fueled by this favorite childhood treat.

"I think everyone has a good childhood association with doughnuts -- partly because even as a kid, you get to pick your own type or flavor, and the whole doughnut is yours. They aren't a 'special occasion' frilly dessert like a cupcake or a slice of layer cake. Any day can be a doughnut day!

"So, in the same way that adults are dressing more and more like their kids (what 40-something dad in the Bay Area doesn't still cherish -- and wear -- his collection of once-cool band T-shirts?), so the doughnut is getting a makeover, going vegan or gluten-free, getting dressed up with fancy glazes, posh fillings and sophisticated flavor combinations. And now they're 'cool.'"