Usually, niché players are satisfied to pull small shares away from the category leaders.

And usually, category leaders overlook the incursions.

Only rarely does the niché grow to challenge the entire category, but this is exactly the case with yogurt.

Until recently, yogurt sales in the U.S. have been dominated by Dannon and Yoplait. Now, Greek-style yogurt, hardly a presence four years ago, dominates.

And New York-based Chobani is the niché-turned-category leader, having launched only four years ago. Greek company, Fage, also led the revolution. It began importing its product in 2000 and opened its U.S. plant in 2008.

Thicker than regular yogurt, Greek yogurt is higher in protein and lower in fat, an appealing combination to health-conscious consumers.

According to a story in The New York Times, “National retail sales of the thicker style of yogurt more than doubled last year, jumping to $821 million for a 52-week period ending in October, excluding Walmart stores.”

The explosiveness of the growth caught the big boys off-guard. “I think we all saw this thing coming,” Sergio Fuster, Dannon’s Senior VP-Marketing, told Ad Age, “but the doubt on the size that it would take probably is what created the difference in the speed of the different companies in approaching the markets.”

Now, they’re playing catch up. Dannon (which introduced yogurt to America in the 1940s) and Stonyfield confusingly offer Oikos and Oikos. Dannon also makes a Greek version of Activia. Yoplait offers its own version and Kraft has added yogurt back to its Athenos line.

Will upstart Chobani hold the lead it captured? Will the giants, now aroused, win it back? A few of the competing TV spots are below.