Diablo 3's first expansion, Reaper of Souls, has entered closed beta testing; opt-in now for a chance to try out the new content before it goes live to all.
According to a handful of helpful resources gathered on Battle.net, applying for beta is as simple as visiting your Beta Profile Settings page and checking the Diablo box - assuming you own the game and have not been banned. After that, it's luck of the draw.
You'll be able to copy your existing characters over, and there's no NDA, so it sounds like a good time for all.
As ever with betas, the product you'll be testing isn't necessarily indicative of the finished product, and Blizzard is anxious to receive your feedback.
Reaper of Souls is expected in 2014 on Mac and PC; it's also coming to PlayStation 4 but has not been confirmed for the PS3 and Xbox 360 versions of Diablo 3.