Justin Bieber and Ariana Grande

Justin Bieber and Ariana Grande have teased a collaboration before, but now there's visual proof that the pair of pop superstars have spent studio time together. On Thursday night (May 1), the Biebs posted an Instagram photo of himself standing next to Grande's unmistakable ponytail.

"congrats @arianagrande on your number 1 song. #arianabieberduet ??" Bieber posted as a super-sneaky caption. The photo finds Bieber looking particularly emotional in the studio -- perhaps the upcoming collaboration is just that moving?

Listen To Justin Bieber's New Song 'We Were Born For This'

"I know that Justin wants to write [a song] if we're going to do something," Grande told Billboard in October when asked about a possible Bieber collaboration. "So it can't just be me being like, 'Hey, do you like this?' He has to sit down and take the time to think about it, which is really cool."

Grande revealed to Billboard that her sophomore album is due out in August or September, and its lead single, "Problem" featuring Iggy Azalea, is headed for a massive debut on next week's charts. Grande's follow-up to last year's "Yours Truly" will feature collaborations with Zedd, Rodney Jerkins and Max Martin, while a collaboration with Chris Brown, for his upcoming "X" album, has also been recorded.