5. Fifth Harmony: 21 Under 21 (2014)

Victoria Stevens
Fifth Harmony photographed by Victoria Stevens in New York on July 9, 2014.

21 Under 21 Main Page

Birthdates: Allyson Brooke Hernandez, July 7, 1993 (Age: 21); Normani Kordei Hamilton, May 31, 1996 (Age: 18); Lauren Michelle Jauregui, June 27, 1996 (Age: 18); Karla Camila Cabello, March 3, 1997 (Age: 17); Dinah Jane Hansen, June 22, 1997 (Age: 17)

Last Year's Rank: No. 21

Why They're Hot: Do you hear that sound? That's the squeal of a million Harmonizers, one of the most passionate online fanbases today, helping the ladies of Fifth Harmony continue thriving a few years removed from their X Factor introduction. Following their debut EP release last October, Fifth Harmony has spent much of 2014 on the road supporting artists like Demi Lovato and Austin Mahone on tour, scooping up fans while readying their debut full-length album, Reflection. The first single, “Bo$$,” flaunted a rhythmic new sound and became 5H’s biggest Hot 100 hit to date, ahead of Reflection’s November release. Although the U.S. version of The X Factor no longer exists, Fifth Harmony -- a pop quintet with real promise -- may prove to be the show’s lasting legacy.

21 Under 21's Next Class | Top 21 Songs by Under-21 Singers 

Billboard's 2014 21 Under 21 List