On Sept. 29, 1998, OutKast dropped not only their best album but also one of the most important albums in music history, Aquemini.

Earthy, worldly-wise, weary, and enshrouded in the warmth of their own psychedelic, futuristic production, the album is a defining moment in their storied legacy. Following the release of ATLiens, which stands as a definitive Hip-Hop classic, Big Boi and Andre 3000 found themselves in a space that traditionally breeds the best art. They'd grown as artists, and with that growth, had to shake off expectations for what artistry should entail. Clutching at freedom in the midst of a life transition is never easy, but it often creates the most poignant, relatable art. Such is the case with Aquemini.

Big, Dre, and Mr. DJ handled all of the production, creating a cocoon for their vision to flourish. Still, it remained grounded and relatable, which is partly what makes it so great. It's familiar and innovative all at once, and 25 years after its release, has managed to sound as fresh today as it did back then.

On the 25th anniversary of the album, we look back at a few of the reasons it's still one of the greatest albums of all time.

Andre 3000 and Big Boi got completely comfortable in their creativity.

There's no doubt that their 1994 debut, Southernplayalisticadillacmuzic and sophomore album, ATLiens, are two of the most innovative, creative records Hip-Hop has ever produced. But while Southernplayalistic... was a crew effort, anchored by the talents of Organized Noize and the rest of the Dungeon Family crew, and ATLiens is where Big and Dre journeyed creatively and discovered their voices as individuals and as a unit, Aquemini is the album where they'd completely arrived in the space they occupy today. They spend time on the album addressing questions about the group's future and style, most prominently on "Return of the "G"," when Dre rhymes, "Then the question is Big Boi what's up with Andre? / Is he in a cult? Is he on drugs? Is he gay? / When y'all gon' break up? When y'all goin' wake up? / N-gga I'm feelin' better than ever what's wrong with you? You get down!"

They perfectly merged their styles: Aquarius + Gemini.

It was important for Dre and Big to showcase exactly how their individual styles and sense of musicality merged to create a sound that has yet to be emulated. Aquemini is the album where that idea is brought to sonic life. The title is a literal merging of their zodiac signs, Big's Aquarius and Dre's Gemini, a blaring answer to the nagging questions about what exactly was up with them following the 1996 release of ATLiens.

"That’s what makes the group so unfuckwithable. You have two sides of the same coin with different points of view. The shit fun, man," Big explained in a 2016 interview.

You can hear how comfortable they are in their art throughout the entire project, even though it's most often intertwined with a sense of weary urgency.

"Even the sun goes down, heroes eventually die/Horoscopes often lie and sometimes, "Y"/Nothin' is for sure nothin', is for certain, nothin' lasts forever/But until they close the curtain (y'all know)/It's him and I, Aquemini..."

“With Big Boi standing by me I knew I had to address some of the shit 'cause I can't have my homeboy looking bad," Dre told Creative Loafing years after the release. "I knew a lotta people felt like Southernplayalistic was some of our hardest work and they felt like we strayed from that. So 'Return of the Gangsta' was trying to give them a sense of, 'Hey, I'm still a regular person.' At the end of the day, you've still got to go through the same neighborhoods so sometimes you have to say stuff to let people know what it is. I'm a man so you can't say some of this stuff to me. The things in that verse were addressing all of that.”

They emerged as producers.

There’s a reason why the albums from OutKast, and truly the whole Dungeon Family, have such a timeless vibe—it’s because their sound was one-of-a-kind, nearly impossible to replicate, keeping it from saturating the airwaves and getting dated. While Organized Noize produced all of Southernplayalistic... by the time ATLiens dropped, Big and Dre had learned from Rico Wade, Sleepy Brown, and Ray Murray, and began producing themselves. Two years later, on Aquemini, their growth as producers was even more evident, and they handled the bulk of the production on album, along with Mr. DJ, setting them up to handle the entirety of the production on subsequent albums including Stankonia and the diamond-selling Speakerboxx/The Love Below as Earthtone III.

Their sound on Aquemini was both space age and nostalgic, and wholly their own.

"Being an alien is just being yourself, when people don't understand you," Dre explained in 2014, when the duo embarked on one last tour. "We just trying to let everybody know there's a place for everybody in this world. You just gotta find yourself, and be true to yourself. That's how you get prosperous and happy."

They proved they're two of the best lyricists in rap history.

There are too many quotables on this album to name — from their superior showing on "Skew It On The Barb-B" with Raekwon to "SpottiOttie..." to "Return of the "G"," "Liberation," and "Da Art of Storytellin' (Part 1)" — the gems on this record are bountiful.

With Aquemini, OutKast delivered not only the definitive album of their career, but one of the greatest albums of all time.