Hip-hop heads at large are rejoicing at the official reunion of Jay-Z and his former mentor Jaz-O. The uninitiated (or younger generations) might not be as familiar with Jaz-O and the role he played in Jay-Z's career. Here’s a brief run-down on why their recently announced Roc Nation deal is a historic one.

(1980s) Marcy Men
Shawn Carter and Jonathan Burks met as kids in Marcy Projects and quickly bonded over their love of rhyming. “I connected with an older kid who had a reputation as the best rapper in Marcy,” wrote Jay in his 2010 book Decoded. “Jaz was his name—and we started practicing our rhymes into a heavy-ass tape recorder with a makeshift mic attached.” They would freestyle and battle for hours together, pushing the limits of one another’s vocabularies and backing each other up in local battles on the block.

(1986) High Potent
In 1986, Jaz and Jay teamed up to form the short-lived duo High Potent, releasing the single “H.P. Gets Busy” to little success.

(1989) “Hawaiian Sophie/The Originator” 
Jaz got the first big break of the two, securing a solo deal with EMI, which released his debut Word to the Jaz in 1989. Jaz kept Jay by his side as a hype man and partner-in-rhyme throughout his deal, putting young Hov on his early singles “Hawaiian Sophie” and “The Originators.”

(1989) London
As part of his EMI deal, Jaz went on a trip to London to record his new album. Jay made the trip along with a young Irv Gotti, narrowly avoiding a federal raid back in the U.S., which he says would have prematurely ended his rap dreams without a reasonable doubt. “Up until that (London trip), my life could be mapped with a triangle: Brooklyn, Washington Heights, Trenton," Jay wrote in Decoded. Jaz’s deal fizzled, but Jay used the experience as a lesson about how ruthless the industry is to artists.

(1996) “Ain’t No N*gga”
Jaz isn’t just a rhymer, he’s also a great producer. His resumé includes tracks for Rakim, Kool G Rap and M.O.P. But his most famous beat was made for Jay’s first breakthrough hit, “Ain’t No N*gga.” Legend has it, Jaz flipped the “Seven Minutes of Funk” sample in one take, hitting each beat on the sampler live through the entire four-minute recording.

(1996) “Bring It On”
Jay-Z’s debut, Reasonable Doubt, featured a verse from Jaz, who was still trying to bounce back from his E1 failure. On the hustler’s classic “Bring It On,” Jaz showed he could still go bar-for-bar with his protégé, and Jay showed he hadn’t forgotten his roots.

(1997) “Rap Game/Crack Game” 
Jaz produced another underground favorite on Jay’s sophomore release, In My Lifetime, Vol. 1, drawing on similarities between the drug and music industries.

(1998) “N*gga What, N*gga Who (Originator 99)” 
In 1998, Jay-Z became a superstar with the success of “Hard Knock Life (Ghetto Anthem)” and his third album, Vol. 2… Hard Knock Life. Ten years after their trip to London, Jay and Jaz made their mark on the Billboard charts with the help of Timbaland’s hypnotic drums on “N*gga What, N*gga Who?”

(2001) “Ether”
Jay’s historic beef with Nas poured gasoline on the flames that were already flaring between Jigga and his former mentor following the success of “N*gga What.” Nas mentioned Jaz multiple times in his battle with Jay, accusing Jigga of biting Jaz’s name and style and mocking his “Hawaiian Sophie” days as Jaz’s sidekick.

(2002) MTV News 
By 2002, Jaz was fed up with his former protegé’s lack of involvement in his stalling career. When Jay only contributed one verse to Jaz’s new album and failed to show up for the song’s video shoot, the former friends officially became foes. “Everything that I did for him as far as his career, I did all of those things to be an agreeable person," Jaz-O told MTV News in 2002. "The feeling just wasn't reciprocated in the way that I understood it. I feel that there is a code to friendship, and I never thought that we would do things together in the business as business. I thought it was all personal, that we were on the same page. Obviously we weren't.”

(2002) “Get High (Freestyle)"/"Blueprint 2" 
Jay took the public complaints in stride, casually mentioning Jaz in subliminal bars and freestyles aimed at more famous foes: “I'ma let karma catch up to Jaz-O,” spit Jigga dismissively on the 2002 tracks “Get High (Freestyle)” and “Blueprint 2” while focusing most of his energy on Nas. Jaz came back at Jay on the track “Ova Pt. 2,” another freestyle that got underground respect but not much mainstream replay.

(2008) “I Do It for Hip Hop”
Jay continued throwing shots at Jaz over the years in songs and interviews. On Ludacris’ 2008 track “I Do It for Hip Hop,” Jay spits, “Shout out to Grandmaster Flash and to Caz/ And even Jaz bum-ass.” Jaz responded with “Go Harder,” a freestyle over Jay’s “Brooklyn Go Hard.”

(2009) “What We Talkin Bout” 
“Dame made millions, even Jaz made some scraps, he could've made more but he ain't sign his contract,” Jigga rhymed about Jaz again on his Blueprint 3 intro. Following the release of Decoded, it was revealed that their issues originated from a $300,000 deal Jay offered Jaz to sign with Roc-A-Fella Records around 2002. Jaz has said he refused because he did not want to go into business with Jay’s former partner Dame Dash. At the time, he sent back shots directly at Jay on The Game’s “Gangstas Ride.”

(2017) 4:44 
After years of radio silence, Jay and Jaz reunited publicly backstage at Jay’s 4:44 concert, setting the stage for their recent deal.

(2019) Roc Nation
In April 2019, Jaz announced a distribution deal under Hov’s Roc Nation label. The deal gives Jaz’s Kingz Kounty Media Group “Equity Distribution” through the Roc Nation imprint. Earlier this week, the deal and its details were officially announced, putting a happy ending on their journey through the music biz.

(2019) What’s Beef
In an interview with VLAD TV, Roc-A-Fella co-founder Biggs Burke explained that the feud between Jay and Jaz was never serious enough to be labeled as “beef.” “Beef isn’t I’m throwing a little shot at somebody on a song. Beef is, when you see them on that block, you either don’t want to walk on that block, or if you walk on that block there’s gonna be a problem between you two. That’s beef. [Those raps], that’s some hip-hop sh*t.”