Niall Horan

When Katy Perry was serving as a judge on "The X Factor" back in 2010, she put Niall Horan through to the next round and told him, "Don't let us down." Three years later, the young Irish singer has done anything but. As one-fifth of unstoppable boy band One Direction, Niall -- along with his bandmates Harry, Louis, Zayn, and Liam -- has taken the world by storm. They've sold 19 million singles and 12 million albums, had their first and second LPs debut at number one on the U.S. album chart, and embarked on a string of sell-out global tours that have confirmed their status as the most successful young band in existence. But how did a self-confessed "emotional guy" from Mullingar, Ireland, become one of the music industry's hottest properties? Illustrated with full-color photos throughout and packed with plenty of behind-the-scenes gossip, this biography charts Niall's rise from hopeful "X Factor" contestant to teen heartthrob and pop superstar.