21 Under 21 Playlist: 5 Seconds of Summer, Fifth Harmony & More of the List's Greatest Hits
![21 Under 21 Playlist: 5 Seconds of Summer, Fifth Harmony & More of the List's Greatest Hits](http://www.billboard.com/files/styles/promo_225/public/media/21-under-21-2015-hero-billboard-650.jpg)
This year's 21 Under 21 list -- our annual look at the hottest artists in all genres who can't yet legally purchase alcohol -- includes bubblegum...
This year's 21 Under 21 list -- our annual look at the hottest artists in all genres who can't yet legally purchase alcohol -- includes bubblegum...