How to do intersection match between 2 DataFrames in Pandas?

Assume exists 2 DataFrames A and B like following

A:

a A
b B
c C

B:

1 2
3 4

How to produce C DataFrame like

a  A  1 2
a  A  3 4
b  B  1 2
b  B  3 4
c  C  1 2
c  C  3 4

Is there some function in Pandas can do this operation?