Industry moguls Dr. Dre and Jimmy Iovine achieved immeasurable success together. Now, their story is revealed in HBO's new four-part documentary series, "The Defiant Ones."

Director Allen Hughes originally set out to make a documentary about Dr. Dre when the explosion of the Beats headphone brand illuminated his longstanding partnership with Iovine. Their relationship stems from their collaborations at Death Row Records, Interscope and later with Aftermath Entertainment.

The two have always had the Midas touch — but "The Defiant Ones" reveals that the journey was full of twists, turns and obstacles.

"This is not a fluff piece," said Hughes on "CBS This Morning." "This is not going to be a tribute film. This is going to be a serious film — the good, the bad and the ugly."

Though each come from different backgrounds (Dre from Compton, Calif., and Iovine from Brooklyn, N.Y.), both ended up as recording engineers. Throughout the '70s and '80s, Iovine paid dues in the studio, engineering recordings for Bruce Springsteen, Tom Petty, Stevie Nicks, and U2. Meanwhile, after creating an undeniable impact on hip-hop in the '80s with N.W.A, Dre moved onto creating his sonic and cultural masterpiece, 1992's The Chronic. Meanwhile,

"When we finally met," says Iovine, "we stuck together [through] some of the most difficult and unnerving times in the history of the entertainment industry."

Together, Dre and Iovine were unstoppable, and the duo provided the firepower behind many of hip-hop's greatest songs and artists since 1992: Snoop Dogg, 2Pac, Eminem, 50 Cent, and many more.

On the merchandising side, Dre and Iovine started an electronics company in 2006, introduced the world to Beats headphones two years later and eventually sold the company to Apple in 2014 for a reported $3 billion.

Anything but formulaic, the success of this legendary partnership is innovative, enduring and undeniable. 

Debuting on July 9, "The Defiant Ones" is the story of that triumph. As music documentaries become more popular and creative, Hughes' film promises to push music industry storytelling forward into a new realm.

Take our poll: What's your favorite current music doc?