At their peak, One Direction were considered the biggest boy band in the world. Today, they're still regarded as one of the most successful boy bands in history, with the likes of the Backstreet Boys and BTS. Despite only being active as a group for five years, One Direction embarked on four successful world tours, made special appearances on shows like iCarly and Family Guy, and released five studio albums, all of which sold a total of 70 million copies worldwide by 2020.