Chris Brown and Rihanna at the Grammys

 Four years later...they're back   

Rihanna and Chris Brown cozied up at the Grammy Awards Sunday, but it was the bling on her left ring finger that really sparked speculation.

Twitter exploded with conjecture that Rihanna — who performed an emotional rendition of her new single “Stay” at Sunday night’s event — is engaged to the man who beat her up at pre-Grammy party in 2009.