<p>princeton professor of history kevin kruse, age 35, is among smithsonian magazine's 2007 "37 under 36," a feature recognizing america's young innovators in the arts and sciences. most of this year's honorees come from outside of academia. kruse, however, very much part of the academy in his post at princeton, is recognized for his provocative research on the migration of mainstream white southerners during and after the civil rights era.</p>