To recap the decade that was, Billboard is looking at one major theme from each year and explaining how it dominated that 12-month period. Below, we start with 2010, a year in which charged-up dance-pop was unavoidable, and Top 40 radio still dominated popular music.

As the 2000s gave way to the 2010s, a relatively unfamiliar artist ascended to the top spot of the Billboard Hot 100 on the first chart of the new decade: Kesha-- or as she was then known, Ke$ha -- with her debut single, "TiK ToK." The song was a rambunctious party-at-all-costs anthem, with a bleating, infectious beat and sung-rapped lyrics about brushing teeth with Jack Daniel's and kicking boys to the curb for not looking enough like Mick Jagger. It was hedonistic, it was vibrant, it was trashy, it was a ton of fun. And if you were looking for a No. 1 hit to set the tone for what pop music was going to be at the outset of the '10s, you couldn't have landed on a much more appropriate choice.

Not that "TiK ToK" was the big bang for the brand of turbo-pop that would blanket radio and hog the top of the charts for much of the early decade: The way had already been paved over the final few years of the '00s. After a long period of Top 40 domination from crossover-friendly lite rock and heavily Auto-Tuned hip-hop and R&B, Lady Gaga struck the mainstream like a lightning bolt in 2008. With barnstorming electro-pop smashes like "Poker Face" and "Bad Romance," and an '80s-indebted vision of all-consuming pop stardom, she became music's biggest new sensation by the end of the 2000s.

THE 2010S WERE THE DECADE THAT...

2011: Adele Revived the Music Industry | 2012: EDM Infiltrated Everything | 2013: Streaming Became Unignorable | 2014: Cultural Appropriation Dominated the Pop Discussion | 2015: 2015 Was the Year That... Canadians Ran Pop Music | 2016: Every Major Album Release Was an Event | 2017: Latin Pop Took Over the U.S. | 2018: Hip-Hop Took Its Victory Lap 2019: Lil Nas X's 'Old Town Road' Put a Bow on the Decade

The next year, conscious MCs-turned-party rap muppets Black Eyed Peas hooked up with French house hitmaker David Guetta for a four-quadrant smash called "I Gotta Feeling." The song was a compulsory sing-and-jump-along that split the difference between Obama-era optimism and post-Recession fatalism, proclaiming that "tonight was gonna be a good night" while implying that today might have been something you really needed to get away from. Following immediately after the 12-week reign at No. 1 for the BEPs' electro-funk throwback "Boom Boom Pow," "Feeling" topped the chart for another 14 frames, setting the radio standard for the decade to come.

The combination of Gaga's starry, personality-driven mega-pop and the Black Eyed Peas' urgently celebratory house-rap would inform many of the biggest artists and singles of 2010. Usher, the former biggest R&B star on the planet who'd fallen on hard times personally and professionally in the late '00s, got an assist from BEPs frontman will.i.am and rebounded to No. 1 with the stadium-ready dance-pop stomper "OMG." Rihanna and P!nk, two of the most reliable stars of the previous decade, both scored their highest-NRG chart-toppers to date with the blazing nu-disco banger "Only Girl (In the World)" and the weirdos-at-the-wedding anthem "Raise Your Glass," respectively. And newcomer Taio Cruz landed two of the year's biggest hits with the glittering, synth-soaked jams "Break Your Heart" and "Dynamite," the latter rivaling even "I Gotta Feeling" for tonight's-the-night revelry.

Amidst all these veterans and rookies, the year's biggest artist was a still-rising star who would find radio's ultimate sweet spot and go on to make chart history with it. Former Christian rocker Katy Hudson had rebranded as secular pop purveyor Katy Perry, and had rampaged onto Top 40 a couple months before Gaga in 2008 with debut album One of the Boys, led by the problematic-but-unignorable ode to bicuriosity, "I Kissed a Girl." That juggernaut quickly plowed its way to No. 1, and follow-up top 10 hits "Hot n Cold" and "Waking Up in Vegas" established her as a force to be reckoned with. But nothing could have prepared fans for the onslaught of sophomore set Teenage Dream, a veritable amusement park of a pop blockbuster fantasia that was a game-changer from its first candy-coated single, the electro-poppy West Coast tribute "California Gurls."

"Gurls" hit No. 1 in July, and was followed to pole position three months later by the set's guitar-led title track, a mid-tempo runaway fantasy that split the difference between Bruce Springsteen and Madonna for a concoction of dangerous pop-rock potency. By year's end, they were met at the top by "Firework," a motivational floor-filler with a chorus as explosive at its title, and over the course of the next year, two more singles joined the club: the stomp-clapping, Kanye West-featuring alien love song "E.T." and the buoyant how-wasted-were-we-last-weekend lament "Last Friday Night (T.G.I.F.)." That made it five total Hot 100 No. 1s for Teenage Dream -- a mark that tied the record set initially by Michael Jackson's Bad from 1987 to 1988, and which no other album has again reached in the years since.

As the sound of Top 40 radio became increasingly uniform in the midst of all these punchy pop smashes, two men emerged as the moment's primary sonic architects. Max Martin had previously reigned as the most impactful writer-producer in popular music at the height of TRL at the turn of the millennium, but had hit a bit of a commercial dry spell in the early '00s. That changed when he met Saturday Night Live guitarist Lukasz Gottwald -- better known as Dr. Luke -- and helped craft Kelly Clarkson's 2004 classic "Since U Been Gone," reviving Martin's career and jump-starting Luke's.

Together and apart, the duo would go on to work on effervescent hits in the mid-to-late '00s for major stars like P!nk, Avril Lavigne and Britney Spears. But their greatest success would come in 2010, through their work with Kesha and Katy Perry, with both men writing and producing on all but one of the latter's five Teenage Dream No. 1s -- the lone holdout being "Firework," helmed by Norwegian duo Stargate, the only behind-the-scenes team with close to the same level of juice as Luke and Martin in 2010.

The turbo-pop peak of 2010 made these artists and producers absolutely ubiquitous on radio -- which, at the time, was still largely unquestioned as the central force of popular music. Though the endless libraries of sites like YouTube, Grooveshark and Pandora had made inroads in siphoning off some of FM's audience, and MP3 blogs and other web tastemakers had gotten the edge on radio in breaking new artists, the impact of Top 40 in minting superstars was still incredibly massive. According to an Arbitron study that December, network radio was still reaching 74% of Americans 12 and up.

The American debut of Spotify was still a year away, and while the ultimate rap giant of the streaming era had started to rise -- Drake had scored a No. 2 hit the year before with the sentimental "Best I Ever Had" -- he couldn't quite hang on the airwaves with the likes of Perry and Gaga yet. Both Drake and ascendant Young Money labelmate Nicki Minaj released their debut albums in 2010 (Thank Me Later and Pink Friday, respectively), but while both were commercial successes, neither notched a Hot 100 single that year higher than the No. 5 peak for the former's shuffling "Find Your Love." Even Kanye, arguably the biggest name in '00s hip-hop, who'd released what most had instantaneously declared his masterpiece that November with the cinematic My Beautiful Dark Twisted Fantasy, couldn't crack the top 10 with any of the set's singles. The charts were dominated by radio, and radio belonged to the pop glitterbombers.

One 2010 pop prodigy did stand as something of a format outlier. On the surface, Justin Bieber's vivacious, treble-heavy bubblegum -- which had made early inroads on the Hot 100 the year before with the top 20 hits "One Time" and "One Less Lonely Girl" -- seemed of a sonic piece with the Taio Cruzes and Ushers of the world; the latter artist even served as an early mentor to the Canadian teenager. But unlike most of the stars of the era, Bieber's true breakthrough did not come via radio, but the Internet: His fanbase swelled to phenom proportions before he even had a single out, thanks to his devoted followings on YouTube and Twitter.

And while Bieber became a household name as a heartthrob, he was mostly ignored on the airwaves at the time: Thanks to huge digital download numbers, "Baby" shot to No. 5 on the Hot 100 and became an early signature hit, but it never rose higher than No. 16 on Billboard's airplay-based Radio Songs chart. Nonetheless, his viral success would continue to grow, and along with rising rappers like Drake and Minaj, his cultural impact would quickly dwarf most of the artists getting incessant Top 40 play, showing a new path to pop superstardom.

For the first few years of the 2010s, most of these stars of radio would continue their chart supremacy. Lady Gaga scored her longest-reigning No. 1 in 2011 with comeback single "Born This Way," Katy Perry would follow the five No. 1s of Teenage Dream with another two off 2013 follow up album PRISM (plus a bonus one in between on her Complete Confection reissue of Dream) and "TiK ToK" was just one of ten top 10 hits Kesha would score in the decade's first half. Meanwhile, Pitbull, Flo Rida and LMFAO would take the Black Eyed Peas' example to ever-goonier heights with high-voltage, brain-fried club rap that flooded radio rotations, party playlists and commercial blocks.

But with the rise of EDM in the years to come, the influence of dubstep and progressive house on the sound of pop music would make it louder and more dynamic, with lurching drops and euphoric instrumental releases often filling in where massive singalong choruses once stood. Later in the decade, the streaming-abetted dominance of hip-hop would turn the BPM down on pop music in general, and make rappers into monocultural figures as impactful -- and often more -- than the biggest singers of the moment. Eventually, the compact, speaker-bursting turbo-pop that defined 2010 would slowly open up its stranglehold on Top 40.

Another unignorable factor in the sound's fade in the eventual mainstream was the dramatic fall from grace of Dr. Luke. While rumors of conflict between Luke and longtime creative partner Kesha had long rumbled in the pop world, particularly following the release of her underwhelming second album Warrior -- leading to a 2013 "Free Kesha" fan movement -- in 2014, Kesha sued her writer/producer and label boss for sexual assault and battery, accusing him of drugging and sexually abusing her. Luke denied the allegations and counter-sued, but much of the industry (and most of his other former collaborators) sided with Kesha. Within a few years, Luke was almost completely absent from the charts, Max Martin had once again reinvented his sound with a new class of hitmakers (including Ariana Grande, Taylor Swift and The Weeknd) and the sound that the two men owned the early part of the decade with all but vanished from radio.

At decade's end, a great deal of affection remains for this boom period in so-called "pure pop," as evidenced by the recent success of artists like Ava Max and Kim Petras, whose glitzy, synth-heavy bops call back to Gaga and Perry's peaks a decade earlier. Such a narrowly Eurocentric, dance- and rock-oriented view of pop has the dangerous tendency to exclude the countless ways in which hip-hop and R&B have informed and advanced popular music over the last 40 years, however, and in the late-decade success of hybrid stars like Ariana Grande, Post Malone and Khalid, it's increasingly unclear what "pop" means as its own genre anymore. (Also, in the cult popularity of Petras remains a hard truth to reconcile: Part of the reason her music so successfully evokes turn-of-the-decade pop is because it's shepherded in part by Dr. Luke, a regular writer for Petras and a persistent presence in the industry, if no longer an omnipotent one.)

However, on the other side of things, Kesha eventually emerged from her legal woes -- which prevented her from making music outside of her relationship with Luke and his imprint, Kemosabe records -- in 2017, with her third album Rainbow. The music bore little similarity to the in-your-face (and various other body parts) dance-pop that brought her to stardom, instead opting for a rootsier mix of rock, soul, country and folk, albeit with the same kind of confrontational attitude that made her such an exciting presence earlier that decade. The most directly confrontational song was "Praying," a piano-led power ballad that served as a rejoinder to her former mentor, and declared, "I'm proud of who I am."

Rainbow topped the Billboard 200, and both single and album drew her best reviews to date, also earning her first two Grammy nominations, for best pop album and best pop vocal performance. It wasn't as big an FM hit as her early singles -- "Praying" peaked at No. 13 on Radio Songs -- but it was still arguably the biggest triumph of her career.

Next, in 2011: An unexpected star goes against radio trends and finds success massive enough to nearly redeem a flagging music industry.