They're on, they're off, they're on. Justin and Scarlett -- make up your freakin' minds already. Seriously!

Justin got his sexy back with Scarlett this weekend in Miami, In Touch Weekly reports. After a 3 a.m. meet-up on Saturday at Justin's hotel room, excuse us -- bungalow, at the Delano hotel, "they spent the whole weekend together," a spy for the mag says. After the Super Bowl on Sunday, the reunited lovebirds hit a star-studded after-party. "They were dancing and whispering in each other's ears," an In Touch source says. "They were having a really good time together." Not such a good time that they stayed 'til the end -- at 3:30 a.m., the couple slipped out the back door hand-in-hand and went back to Justin's hotel for the night. "As they left through the back, Justin was leaning against the wall and Scarlett came up, leaned into him and did a sexy, little dance, grinding into his body," a source for Page Six reports. We guess this means bye-bye, Biel!

OK, you may not have been there to witness the heat between Justin and Scarlett, but you can certainly feel it in this clip for Justin's new video for "What Goes Around... Comes Around."