The smallest fast-casual pizza concept on the list has a rep as a cool kid on the block. The bike-friendly chain leads group rides and offers 20% off pizza after the workout. Spin teams up with craft brewers for beer and gelato pairings and hosts sip-and-paint art sessions on its patios. It has zeroed in on millennials, opening units at Southern Methodist University in Dallas and University of Central Missouri in Warrensburg, Mo., and offering barrel wines, happy hours and small plates, while maintaining an average check of $12.

LocationKansas City, Mo.
2015 Systemwide Sales$26,000,000*
% Change in Sales73.3%
2015 U.S. Units18
% Change in Units80.0%
2015 Average Unit Volume$1,860,000*
% Change in AUV-0.8%
Future 50 Year2016