It's Britney Spears circa 2003, b**ch.
The "Slumber Party" singer posted a sexy throwback photo on a Sunday, as opposed to a Throwback Thursday or Flashback Friday. (Hey, we don't mind.)
RELATED: Britney Spears Has a Racy 'Slumber Party' in Sexy New Music Video With Tinashe
Spears took to Instagram to share a glimpse at her In The Zone-era body -- a throwback shot from that epic topless Mark Rolston photo shoot for the October 2, 2003 issue of Rolling Stone. You know the one.
"My friends sent me this picture today… and it's weird because I just realized it's one of the only pictures I've ever taken upside down!" the 34-year-old captioned the revealing snap.
The racy photo from the same era that brought us "Toxic" isn't such a far cry from Spears' current physique, as she recently told Ryan Seacrest that she is the fittest she's been in "probably 20 years."
RELATED: Britney Spears Reveals the Perks of Photoshop: 'I Might as Well Eat Six Pieces of Pizza'
That would explain why Spears has taken to sharing more scantily clad shots in recent months, along with releasing the sultry music videos for "Slumber Party" and "Make Me."
MORE: Britney Spears Makes Out With Shirtless Hunk in Steamy 'Make Me' Music Video
When you're a smokin' mother of two with abs like that on the week of your 35th birthday (B's birthday is December 2nd!), we say it's allowed. For even more Britney, watch the clip below.