Though the couple first met on The Mickey Mouse Club in 1992, Britney and Justin didn't go public with their relationship until 1999.
"It is a deeper love now than when I was younger. Like, we've gone through so much together and we've known each other since we were 12 years old. We know each other inside and out," Britney told The Observer.
The pair went on to perform at the 2001 Super Bowl Halftime Show together and rock those iconic denim on denim outfits at the American Music Awards that same year.
However after they ended things in 2002, things turned ugly.
In the wake of their split, Justin appeared on various televised interviews to promote his new solo career, but ended up discussing his ex with very personal details.
His now infamous interview with Barbara Walters featured him denying that any songs on his new album were about Britney, but he then played a song called Horrible Woman that featured lyrics including: "I thought our love was so strong / I guess I was dead wrong / But to look at it positively, hey girl / At least you gave me another song about a horrible woman."
Justin then outright laughed when asked if Britney had kept her promise to wait until marriage to have sex.
Meanwhile when Diane interviewed Britney on the same topic, the TV reporter asked: "He has gone on television and pretty much said you broke his heart. You did something that caused him so much pain, so much suffering — what did you do?"
2002 saw the release of Justin's hit Cry Me A River that reportedly alludes to Justin finding out that Britney was cheating on him with a choreographer they both knew.
The music video even features a woman who looks remarkably like his ex and the Framing Britney Spears interviewees suggest that the video and the accompanying promotional tour, was a way to market Justin as the innocent, heartbroken guy and Britney as an unfaithful villain.
A year later, Britney released her ballad Everytime which is thought to be a response
"I may have made it rain / Please, forgive me / My weakness caused you pain / And this song's my sorry," the lyrics of one verse say.
Then in 2006, Justin released another revenge song What Goes Around . . . Comes Around that coincided with the start of Britney's personal struggles including several clashes with the paparazzi and the end of her marriage to Kevin Federline.
During his press tour for the FutureSex/LoveSounds album, Justin confirmed that Cry Me a River"was about her in GQ, explaining: "I felt like she had a couple of opportunities to just sort of stick up for me, and she didn't. Which is ﬁne. But at that time, you know, I fought back, and that's the way I fought back. I used my mind. I came up with a song."
These days, there appears to be no bad blood between the former exes.
Whilst Britney has been dating actor Sam Asghari since 2016, Justin is married to actress Jessica Biel.
Following the release of the New York Times' explosive documentary, Justin has issued a personal apology to Britney and Janet Jackson, the latter of whom was slammed after her 2004 Super Bowl set with Justin when she suffered a wardrobe malfunction whilst her co-performer had seemingly no similar repercussions.
"I've seen the messages, tags, comments and concerns and I want to respond. I am deeply sorry for the times in my life where my actions contributed to the problem, where I spoke out of turn or did not speak up for what was right," he wrote on Instagram.
"I understand that I fell short in these moments and in many others and benefited from a system that condones misogyny and racism," Timberlake continued. "I specifically want to apologize to Britney Spears and Janet Jackson both individually, because I care for and respect these women and I know I failed."
"I also feel compelled to respond, in part, because everyone involved deserves better and most importantly, because this is a larger conversation that I wholeheartedly want to be part of and grow from … "