Britney's back -- and she's working, bitch.
On Sunday, Spears posted a photo of herself in a tiny blue bikini, and sky-high sparkling heels, to her Instagram account, which she captioned:
"Gonna get my tan on in the desert in between shots on the #WorkBitch set today. It's HOT out here people!!!! #desert #heatwave #WorkBitchDay2"
"Hot day on set... ;) A little dirty, little flirty, danced my ASS off. Stoked for tomorrow!"