How to make 2d RooDataHist

Hi,

Could you let me know how to construct 2d RooDataHist?

I mean, I have couple of 1dim. RooDataHist, I would like to 2d binned fit, but in my understanding, RooDataHist may supprot TH1F only.

I would be happy if any can let me know the correct access ways.

Cheers,