With their first full-length, Undertow, Tool unexpectedly broke into the alt-rock mainstream. They went platinum, played Lollapalooza's main stage, and their stunning videos for "Sober" and "Prison Sex" earned the band regular play on MTV, thanks to guitarist Adam Jones' visual genius and background in movie special effects. However, on September 17th, 1996, a little more than three years removed from the release of Undertow, Tool took an even more monumental leap, into the psychedelic, prog-metal stratosphere with the release of Aenima.

The title of the album hinted at its content. "Anima" is Latin for "soul" and an "enema" is, of course, a process that flushes out waste from the intestines by injecting saline solution into the anus. Tool's previous EP and album plumbed the darkness depths of the human psyche, but Aenima aimed for soulful inspiration and spiritual awakening — while still retaining some of the group's characteristically sophomoric sense of humor. Musically, Tool took the first major step towards becoming a true progressive-rock band, as song lengths topped the eight-minute mark and the scope of their sonic pallette defied all easily classified genre boundaries.

"The things that excites me artistically with our projects is I'm always thinking, 'Let's do something that's never been done before. How far can we push something?'" Jones said. "We had some longer tunes like 'Third Eye.' We weren't afraid to go and have eight-minute songs, whereas before we couldn't help but think, 'Well, is anyone even gonna listen to this? Are people's attention spans this long?' We finally knew we had a fan base that would invest the time into the album."

Indeed, they did and still do — Tool fans are some of the most obsessive in the world. But for those of us who are more casual acolytes of the band, here are 10 things you might not know about their trailblazing second album.

Video of TOOL - Stinkfist

1. David Bottrill barely knew who Tool were when they asked him to produce Aenima

The first two Tool releases, the Opiate EP and Undertow, were produced by Sylvia Massey. While the band liked her and felt she was a good engineer, they wanted to work with someone more creative and hands-on for their next record. After hearing a David Sylvian/Robert Fripp album that David Bottrill had produced, Tool decided to give him a call. "Frankly, I knew very little about the band," the producer told Firstpost.com. "They contacted me and sent me Undertow and Opiate. I liked it, but as I hadn't really worked on that kind of heavy music too much, I thought that they may have confused me with someone else."

2. The simple fact that Tool were better musicians heading into the writing process for Aenima had a lot to do with the album's newly progressive direction

By the time the band finished touring for Undertow, Tool had played nearly two years of shows almost every night. Doing so made their chemistry stronger and their playing more intuitive. "We just became a lot better craftsmen as players and that changes your sound completely," said drummer Danny Carey. "Once you can have that kind of freedom, an idea will come into your head and you can do it justice. But when you're not a good player, you can have all the great ideas you want, but you can't get them out. Touring so much gave us a lot more impact, a lot more ability to translate our emotions and ideas once we became better players, which automatically came from playing nearly three years on the road."

3. Tool split with bassist Paul D'Amour in part because he didn't want to play bass anymore

"When we were writing for Aenima, Paul was starting to get frustrated about not playing enough guitar," Carey explained. "He really wanted to be a guitar player in the band even before we started on Undertow. He wanted to hire another bassist and we were all just like, 'There's no way we're getting another asshole in this band to deal with.' So, Paul was trying to push for other things, and as a byproduct, maybe he wasn't working as hard on the songs that we were working on. It got to a point where everything almost ground to a halt. That's when we let Paul go. And then we had to spend four or six months just going through people trying to find a replacement for Paul."

4. Tool auditioned some great players before they found bassist Justin Chancellor, who would play on Aenima and all their recordings since

The band didn't necessarily want to replace D'Amour with a well-known bassist; they were more interested in finding someone that was dedicated and open to experimentation. Along the way, they auditioned Scott Reeder (Kyuss), Frank Cavanagh (Filter), Shepherd Stevenson (Pigmy Love Circus) and numerous others before inviting Justin Chancellor, who was a member of a U.K. band called Peach that had opened for Tool in the early Nineties, to fly in from England and try out. "Justin was the missing link for Tool," Jones said. "We tried out other guys that were really great and maybe even technically better, but Justin had the writing, he had the ideas, he was really artistic and he was really great to get along with. So it was kind of like the new, improved Tool and the other stuff we did was, like, Coke Classic." Added Carey: "Everyone we auditioned knew the songs and played great, but the different thing Justin had going on was his ability to click with us in a freeform jam. We'd go, 'OK, let's just make something up here on the spot,' and when we did that we instantly knew Justin was out guy because he fit in instantly that way."

Video of TOOL: Hooker with a penis live

5. Though he had landed his dream gig, Chancellor didn't find being in Tool all that much fun at first

Being invited to join a celebrated, groundbreaking band that he was already a big fan of, Chancellor was nervous and initially overwhelmed. Tool wanted him to relocate to Los Angeles right away and take over where D'Amour left off, which only boosted his anxiety. "I was confronted with all this new material, which was incredibly challenging and intimidating," he said. "I had just moved to America with only my guitar and clothes, which was very tough on a personal level. And then I went through a long period of time where I was trying to feel confident that the stuff I was coming up with and sharing with them was good. They told me it was worthy and we should start working on it, but it was hard for me to believe them. All that I could think about was the stuff they had already done, which was a benchmark for me. I wasn't a confident person and it was very much a struggle to be comfortable in that situation. It was almost impossible for me to enjoy the experience, which was everything I ever wanted."

6. Tool frontman Maynard James Keenan did extensive research in order to "disintegrate [his past] negativity" with his Aenima lyrics

For Tool's Opiate EP and Undertow album, Maynard James Keenan reached into his past to address such subjects as sexual abuse and the dark side of religion. In order to avoid repeating himself on Aenima and to bring a more positive, forward-looking message into the world, he started doing heavy research and reading to reorient his thinking. "Right around Aenima I was trying to figure out a way to transmute that stuff [I used to write about] and let it go — finding different paths to disintegrate that negativity," he said. "I did a lot of esoteric, spiritual and religious reading. I did a lot of mathematics and read psychological books. Just a lot of introspection, a lot of sound mind, sound body world studies. Somehow, I managed to dodge that third album road stories bullet and take the songs in a more esoteric, spiritual direction while still hanging on to some of the emotions and some of the charged feelings."

7. Keenan also started taking extra-special care of his voice during the making of Aenima

When he was younger, Keenan could drink, hang out with smokers and stay out all night without it taking a toll on his singing. Suddenly, during the making of Aenima, he started paying close attention to what he ate and drank, what environments he was in and how much he used his voice at any given time. The results can be heard on the record. "The best way I can describe it is to use that pregnancy metaphor," he said. "You're all out running around and everyone's like, 'Hey, let's go to this place.' Everybody unconsciously wants to walk into the smoky pub, and here you are, the pregnant woman, standing at the door saying, 'I really can't go in there.' And they go, 'Oh, right. You can't go in there. OK, well, we'll find some place that's not as fun so the pregnant woman can hang out with us.' That's kind of how you start to feel at that point where you realize you've got this responsibility that they don't have. You've got these two little flaps of skin in your throat that are very volatile. And there's things you just can't do, otherwise they just don't work so the sounds don't come out. You can't just buy another piece of equipment to replace it. As time goes on and you get a little older, those weird kinds of tensions start to come out. But once again, art is tension. Art is stress and release. So, those juxtapositions are exactly what make us who we are and between my brothers and I, it's the same thing. You kind of need that."

8. "Hooker with a Penis" isn't just a "fuck you" song

One of the heaviest songs on Aenima, "Hooker with a Penis" starts with hazy waves of guitar before building into a surging, syncopated rhythm. Then, the vocals kick in with short blasts of rage that culminate with a harsh, pull-no-punches tell-off of a chorus, seemingly directed at a self-righteous fan: "And if I'm the man, then you're the man, and he's the man, as well/ So you can point that fucking finger up your ass." Still, the song wasn't meant to be a vicious condemnation of a turncoat diehard, according to Keenan; it's actually about unity. "On the surface, 'Hooker With a Penis' sounds like facing off with somebody and saying 'fuck you,'" the singer explained. "But the song is actually all about us being in this together and us having made a decision to be here and to participate."

Video of TOOL - Ænema

9. "Stinkfist" is kinda about fist-fucking an alternate universe. Kinda.

When Tool released "Stinkfist," the title raise some issues. MTV aired the video, but changed the title to "Song #1." "People immediately hear the title 'Stinkfist,' and they hear some of the words and they assume it's all about one thing — they can't make the leap, explore what else it might be, what other implications it has," Keenan said. "They're assuming right away that it's about fist-fucking. Of course, that would be the comic side of it, but it's not really about that at all. It's about alternative perspectives, about desensitization. It's about how you kind of have your back turned to alternative ideas. It's like that scene in Stargate where James Spader is sticking his hand through the Stargate and he's kind of moving into that next world. First you're finger deep, knuckle deep, elbow deep, move into this whole new perspective. This whole other reality of the sensual and physical. That's the thread that pretty much sows the whole album together, this idea of evolution and change and alternative perspective."

10. The title track is about L.A. falling into the ocean, but it's also about "what really matters"

The album artwork for Aenima included a lenticular image of the West Coast of the United States in which California disappeared when the picture was viewed from a different angle. The idea of Los Angeles being washed away by a series of catastrophic geological events appealed to Keenan, at least on a philosophical level. "On the surface it looks like, perhaps, we're just saying California is this Sodom and Gomorrah that needs to be wiped away," he said. "But you really need to consider the way our economic and political systems are set up. If something were to happen to Los Angeles on a major scale where it just got taken out of the picture, within 48 hours the world's economic system would really have a hard time if not collapse completely. They're so intertwined. So the song is kind of a metaphor for what really matters. Do you really need your Porsche? Do you really need all these things to evolve who you are? Perhaps the next step of evolution would be the next piece in us that the children that we're bearing today already have. Maybe they're going to grow up understanding that unity inherently."