Guess what franchise concept is red hot By: CNBC.com News March 20, 2015 at 10:30 AM EDT Personal-service franchises that appeal to millennials are one of the industry's fastest-growing sectors. They debuted the most brands in 2014. Read More >> Related Stocks: Chipotle Mexican Grill Dunkin' Brands Group Nordstrom Shake Shack Inc Zoe's Kitchen Inc