We've got the scoop.
The obvious suspects, like BFFs Vanessa Hudgens and Ashley Tisdale, follow each other on the social networking site (they're in a lot of each other's photos as well), and the Kardashian/Jenner clan make sure to follow each other too.
But, not all celebs are as Insta-follow friendly.
As it turns out, Victoria Justice isn't following any of the guys on her summer tour, but she does make sure to regularly gives them shout-outs on Instagram, according to ClevverTV.
And although Harry Styles follows Justin Bieber, the Biebs is not following the One Direction singer back. This might not be an intentional snub, though, considering Justin isn't even following his own manager, Scooter Braun, on Instagram either (Justin's mom, Patty, is following Scooter, however).
Speaking of Harry, he is still following his ex-girlfriend Taylor Swift on Instagram following their break-up, but she's not following him back.
To find out more about who's following who on Instagram, check out the clip above!
Gallery | One Direction's Instagram: Best of Harry Styles