Marie Kondo, 31
Professional organizers have long preached the emotional benefits of decluttering the home, but it wasn’t until Kondo that the subject became a global fixation. Her organizational advice comes with instructions as quirky as they are precise. You should hold your belongings one by one: If an item “sparks joy,” keep it; if not, thank it for its service and let it go. Her KonMari Method has attracted legions of fans, and her breakout book, The Life-Changing Magic of Tidying Up, has been on the New York Times bestseller list for 99 weeks.