Billboard is celebrating the 2010s with essays on the 100 songs that we feel most define the decade that was -- the songs that both shaped and reflected the music and culture of the period -- with help telling their stories from some of the artists, behind-the-scenes collaborators and industry insiders involved. Since the introduction of digital downloads in the early 2000s, seven songs have crossed eight million in sales as of September 2019. Many are easily definable – there’s Macklemore & Ryan Lewis’ goofy, sax-drenched pop rap of “Thrift Shop,” Adele’s “Rolling in the Deep” and its infectious stomp-clap beat, the club-ready dance-pop of the Black Eyed Peas’ “I Gotta Feeling,” the only song of the bunch to broach 9 million downloads. That’s not to say Imagine Dragons’ “Radioactive” isn’t in the same boat, but let’s say it had one foot out of it. Toward the end of summer 2012, the Dan Reynolds-led Las Vegas rockers had one hit to their name, a quirky, affirming, mandolin-forward single called “It’s Time” that became a major alternative hit, and crossed over to the Hot 100 as well, peaking at No. 15.

Then roared in “Radioactive,” with a bass-shaking thunderclap that didn’t just dwarf “It’s Time” – it also sounded unlike anything of its time. A then-still-guitar-heavy alternative format was faced not so much with Wayne Sermon’s six-string riffs as it was room-vibrating percussion and distorted electronic stabs that recalled pop radio’s flavor of the week, dubstep. Credit Manny Marroquin, the song’s mixing engineer, not only for helping create that sound but also implementing the dynamics that made the song stand out to begin with. “The key was to make the low end and the sub really, really jump out,” Marroquin says. “I remember when [the first verse] hit, [I thought], 'This is the moment where it's gotta really slap.'”

Marroquin also says that he and producer Alex da Kid, both of whom had worked extensively on multiple hip-hop and R&B tracks prior to pairing for “Radioactive,” wanted to incorporate hip-hop elements to the point that a certain then-fledgling rapper might seamlessly hop on the song’s remix. “Alex and I had a lot of discussions about, how would we make it sound so that Kendrick Lamar would jump on it?” Marroquin recalls. “So that was the bar, you know?” Co-writer and recording engineer Josh Mosser, meanwhile, explains that the song is “literally hooks upon hooks … Now set the melody and lyrics over top of an infectiously good backing track, which has its own hooky parts, and you have something that people will continue to go back to and enjoy over and over again.” He adds that the chorus itself was a Frankenstein-esque merging of two different melodies mashed into one super chorus.

READ MORE Imagine Dragons: The Billboard Cover Story “Radioactive” proceeded to rule Billboard’s Alternative Songs chart for 13 straight weeks from March 2013 to the end of May. At the time of its initial reign, it displaced a fellow early adopter of the 2010s-flavored alternative/electronic fusion, Muse’s “Madness,” a song that truly leaned into its dubstep influences and turned the wubs up to 11. Meanwhile, a predecessor, Alex Clare’s “Too Close,” was practically two different songs: plaintive singer-songwriter on the verses, club banger on the chorus. “Radioactive” instead blended these sounds more deftly, creating something palatable to alternative and pop fans alike. By the end of its radio run, it appeared on a wide array of different formats, from Mainstream Rock Songs to Rhythmic Songs. In some ways, that formula persists. Threads of “Radioactive” can still be heard in a weekly perusal of Spotify’s New Music Friday playlist, represented in songs that are just enough this genre while also being a little that genre to appeal to as wide a demographic as possible. To that end, Marroquin refers to the blend of musical threads found throughout the song as “almost the beginning of genre-less music” -- an opinion that holds weight more than ever at the close of the decade, when artists often leap from radio format to radio format without as many of the barriers that might have previously stood in their way. READ MORE Imagine Dragons: Who Wants to Talk About the Biggest Band of 2017? Imagine Dragons themselves pulled off the trick again with 2017’s top five Hot 100 hit “Believer” and “Thunder,” which in many ways take lessons learned from “Radioactive,” featuring guitar to an extent but mostly defining its sound on blasts of percussion and Reynolds’ muscular vocals. It was little shock when, like “Radioactive,” the tracks were featured prominently in many commercials and TV shows throughout the year.