When Britney Spears and Justin Timberlake ended their three-year relationship in 2002, it took the world by surprise.

They were the undisputed King and Queen of pop music who seemed like the perfect match. She, America’s singing sweetheart; he, the frontman of the popular boy band NSYNC.

But behind their individual successes and their iconic double-denim red carpet look that’s cemented in pop culture history, their relationship wasn’t so picture perfect.

WATCH: Here are a bunch of famous people we absolutely forgot dated! Post continues after video.

Eighteen years on, Britney and Justin have reconnected on Instagram. Reconnected is a very loose term to describe what’s happened here.

In April this year, the ‘Baby One More Time’ singer shared a video of herself doing a TikTok dance to her ex’s 2018 song ‘Filthy’.

“This is my version of Snapchat or TikTok or whatever the cool thing you’re supposed to do these days. As you can see I’m not really dancing folks …… I’m just very bored,” Britney, now 38, captioned the video.

“PS I know we had one of the world’s biggest breakups 20 years ago …… but hey the man is a genius !!!! Great song JT!”

In 24 hours, the post was viewed by three million people, including said ex, Justin Timberlake. The 39-year-old even went as far as to comment a bunch of emojis on the post.

Almost nothing sums up the strangeness of 2020 better than the sight of Britney Spears dancing to a Justin Timberlake song in a crop top and low-rise shorts on Instagram, and Justin commenting on it with praise hand emojis.

These are strange, strange times we're living in. Image: Instagram/britneyspears.

It also made us nostalgic for the story (and photos) of their relationship, so keep scrolling for a deep dive into the pop star power couple’s romantic rollercoaster relationship.

Britney Spears and Justin Timberlake's Mickey Mouse Club days.

Britney and Justin met when they were kids in the late 80s. Both starred in The Mickey Mouse Clubvariety TV show alongside other celebrities including Christina Aguilera, Keri Russell, Ryan Gosling and fellow NSYNC member JC Chasez.

The childhood friends didn't start dating until 1998. Britney was booked as the support act on an NSYNC tour that lasted 18 months, during which time she and Justin started dating.

In happier times. Image: Getty. Image: Getty.

The double denim moment that made pop culture history.

In the years they dated, both Britney and Justin achieved major career success.

Britney became the best-selling teenage artist of all time with her albums...Baby One More Timein 1999 andOops, I Did It Againin 2000. Justin had further hits as the lead vocalist of NSYNC.

Then, in 2001, the couple wore the most famous double denim outfit of all time to the 2001 American Music Awards. The outfit - her sweetheart-neckline denim dress and low-slung belt, and his full denim suit and matching denim fedora hat - has been recreated thousands of times at Halloween and fancy dress parties. Even Katy Perry paid homage to the look at the 2014 MTV VMAs.

Who could forget this iconic 2001 American Music Awards outfit? Image: Getty.

Britney and Justin's shock breakup andthatrevenge song.

Justin and Britney's 2002 breakup was a shock, mostly because the general consensus was they'd get married and have child star prodigy children.

Just before Britney's big screen debut in the vastly underrated filmCrossroads(in this writer's opinion), their relationship ended abruptly. There have always been rumours Britney had an affair with choreographer Wade Robson, but neither have ever spoken about it publicly.

What came next was a series of revenge songs neither Justin nor Britney said were revenge songs, but 100 per cent were.

Later that year, Justin released the moody ballad 'Cry Me a River', with such lyrics as:

You know that they say that somethings are better left unsaid It wasn't like you only talked to him And you know it (Don't act like you don't know it) All of these things people told me Keep messing with my head Should've picked honesty Then you may not have blown it

And....

You don't have to say, what you did I already know, I found out from him Now there's just no chance With you and me There'll never be Don't it make you sad about it?

Two years later, Britney replied with her own alleged revenge song 'Everytime' in 2004.

The song had a sadder tone to Justin's, with lyrics referring to her still needing someone and a disturbing film clip.

And in 2006, Justin's song 'What Goes Around … Comes Around' was also allegedly about Britney.

It was... a lot. The song's video was a spectacle starring Scarlett Johansson. And get a load of these lyrics.

Now girl, I remember everything that you claimed You said that you were moving on now And maybe I should do the same Funny thing about that is I was ready to give you my name Thought it was me and you, babe And now, it's all just a shame And I guess I was wrong

Britney Spears and Justin Timberlake - their lives now.

After their breakup, Britney's success continued until her highly-publicised 2007 breakdown. In 2003, she kissed Madonna in the infamous VMAs performance. In 2004, Britney decided to marry Jason Alexander, one of her childhood friends. The couple got hitched at The Little White Wedding Chapel in Las Vegas. Just 55 hours later, Britney got their nuptials annulled.

In 2004, after her relationship with Jason ended, Britney started dating Kevin Federline, who was one of her backup dancers. They got engaged within two months and then married within the year. Their relationship was chronicled in the reality showBritney & Kevin: Chaotic. The couple had two children together and divorced two years later.

2007 was the year Britney shaved her head and became a viral meme - “If Britney can make it through 2007, then I can make it through today.”

“I was going through so much artificial stuff with my kids and Kevin at the time. He’d just left me and I was devastated,” she toldMTVin an interview for the 2008 documentaryFor the Record.

“People thought that it was me going crazy and stuff like that, but people shave their heads all the time. I was going through a lot, but it was just kind of like me going through a little bit of rebellion, or feeling free, or shedding stuff that had happened, you know?”

Britney eventually lost custody of her children and was hospitalised in a psychiatric ward, where she was held for observation. A judge awarded her father control of Britney's personal and financial affairs. The conservatorship is still in place today.

Britney went on to make a career comeback, going back on tour and taking up a successful Las Vegas residency.