Adam Bielawski · CC BY-SA 3.0

Mike Posner's 2010 debut single 'Cooler Than Me' went septuple platinum and reached No. 6 on the Billboard Hot 100, but he built a second career writing hits for other artists -- co-writing Justin Bieber's 'Boyfriend' and Maroon 5's 'Sugar' among others -- before an EDM remix of his own song 'I Took a Pill in Ibiza' returned him to the top five of the American charts in 2015.