Back before her 1986 breakthrough, “Control,” then-teenage Janet Jackson was still mostly known as Michael’s Little Sister. And being Michael’s Little Sister brought with it a whole range of expectations and allowances. While no one would suggest that growing up a Jackson was without struggles, being the baby of one of the world’s most famous families, one that included six older brothers, certainly helped shield her from some everyday indignities and hassles.

Yet that background did little for her in late 1985, when a pair of men began pestering her at a Minneapolis nightclub. Up-and-coming producers Jimmy Jam and Terry Lewis, who were working with Jackson to create her third album, her first since firing her father as manager, sat nearby and watched. After waiting fruitlessly for her producers to come to her rescue, Jackson finally took matters into her own hands, told off the unwelcome suitors in furious fashion, and approached Jam and Lewis.

As Jam recalls, when she demanded an explanation for their complacency, he immediately turned the situation into a Miyagi-like tutorial.

“You can take care of yourself, girl, you don’t need people to take care of you,” Jam told her, urging her to channel her anger into music. “In life, there will be all these little experiences along the way, and you can put lyrics to them. These are valid ideas: What you’re thinking, what you want to get across, it’s all valid.”

The three quickly wrote the self-reliance anthems “Nasty” and “What Have You Done for Me Lately,” and set the template for the uniquely personal, purgative approach to songwriting that has since come to define Jackson’s career.

It’s difficult to think of another pop star of Jackson’s caliber whose personal development has been so inextricably entwined with her music. For all the millions of albums sold, the hundreds of millions in touring grosses, the film roles, the bestselling book, the brand endorsements and the luxury fur line, there has always been a certain street-level realness to Jackson’s persona, a sense that she could still stand up to anyone in a fight, and probably emerge from the experience a song or two richer.

Her career-making mid-’80s work saw her dramatically evolve from a fresh-faced pop heiress to a tough, self-sufficient young woman. Her subsequent sexual awakening likewise played out in starkly public terms, as Jackson moved from the seductive allure of “Janet” to the loneliness and confusion of “The Velvet Rope” to the outright carnality of “Damita Jo.” Even as a femme fatale, Jackson was honest: Madonna might have been more X-rated, but even her most literally naked moments came with an ironic guard up, while Jackson had no such compunctions.

Not only is it hard to imagine an all-conquering diva like Beyonce or Aaliyah without Jackson’s influence, it’s just as hard to picture the tuneful yet splenetic likes of Pink, Alanis Morrisette and even Usher finding a home on pop radio without her as the model. Yet for all her influence, Jackson is also something of an anomaly in 2013. For one, Jackson has never functioned as a steady-rolling content machine, routinely taking several years between projects. The oft intense intimacy of her music has rarely coincided with an over-shared public life, and she retains a sense of mystery. And unlike the one-shot stars on the contempo pop assembly line, Jackson took her time to get going as an artist.

Despite her familial connections — or perhaps, in fact, because of them — Jackson’s entrance into pop music was hardly auspicious. First album “Janet Jackson” peaked at No. 63 on the charts, while follow-up “Dream Street” couldn’t even break into the top 100.

“I think her early albums were more driven by her dad knowing that she had talent and basically getting her into a record deal,” Jam notes. “So those records were basically this: Some tracks were created for her, she went in the studio and sang them, and she did a fine job. But there was nothing unique about what they were doing.”

With Jam and Lewis behind her, however, Jackson quickly ascended the pop hierarchy. “Control” sounded like nothing else in record stores — full of loud, clipped electronic percussion and insinuating synth lines — while Jackson’s messages of empowerment and chip-shouldered feminism were miles away from the ironic provocation of Madonna or the willful quirk of Cyndi Lauper.

“Control” was an overnight success, notching five No. 1 singles and selling just as many million copies. Unusually eager to tamper with a winning formula, the threesome followed it up with “Rhythm Nation 1814,” a quasi-concept album whose opening three songs directly addressed crime, the crack epidemic, racism, homelessness and youth illiteracy — not exactly a recipe for a party. And yet the record was somehow even more successful, generating a then-record seven top 5 singles.

“The idea of putting ‘Rhythm Nation,’ ‘Living in the World’ and ‘The Knowledge’ as the first three songs on the record really set the tone as to what the record was,” Jam says. “Then to have the segue after that where she says, ‘Get the point? Good. Let’s dance…’ and then go into ‘Miss You Much,’ that was purposely done. In hindsight, maybe we could have called the album “Escapade” and loaded the radio songs upfront, saving the political songs for last. … So if anything was gutsy about it, it wasn’t that we wrote the songs, it was that we featured them.”

Her career would only gain momentum as the years went on, with the tours getting bigger and bigger, a deal with Virgin in the early ’90s breaking records, an entre into film alongside Tupac Shakur in “Poetic Justice,” a rather memorable Super Bowl half-time show appearance, and collaborations with everyone from Chuck D and Busta Rhymes to opera star Kathleen Battle and techno-classical violinist Vanessa-Mae. In the new millennium, Jackson pushed further into contemporary R&B, ever evolving, even if that evolution alienated some.

“I don’t think we agreed with all the ideas that came about as our involvement lessened,” Jam notes ruefully. “And obviously the results were probably less successful in concert with that. So whether you want to put the two things together …”

But Jam’s criticisms have as much to do with protection as personal pride. “To me, Janet is a coveted artist, a coveted asset, you know? And if, as a producer, you can’t really take the time to come up with something that’s great for her rather than just pulling some stuff off the shelf … that’s really disappointing to me.”

Her longtime choreographer Gil Duldulao admits that some of her deep dives into R&B were challenging. “I see her as a pop icon first,” he says. “And if I may say, I think she needs to get back to her lane. Her lane, but in a current way, a way that she could be her again, but still take things to a new level.”

And there’s plenty of time left for yet another chapter in the Jackson story. Rapper Kendrick Lamar’s currently inescapable single “Poetic Justice” has returned 1993’s “Any Time, Any Place” into teenage consciousness thanks to a well-placed sample. Roles in Tyler Perry pics have kept her in the public eye. And per Duldulao, conversations about potential projects are always floating.

“She really thinks a lot about things, like ‘Hey, if I’m going get up and go out there, I’m not going to put music out just to put it out,’ ” he says. “And I see her really changing the game in music again — that’s why she’s taking a long time.”

Greatest Hits: Over the course of her career, Jackson has had 35 No. 1 singles and has sold 100 million albums worldwide. Here is a look at her top-selling studio albums by number of copies sold.