The theory of theta correspondences, which was originated from the work of Roger Howe, has been proven to be extremely successful in the Langlands program. In particular, it allows one to construct (often quite explicitly) representations of one group out of representations of another. In this talk, I will explain the basic mechanism of how this theory works along with some recent developments and discuss some of its applications. Speaker(s): Shuichiro Takeda (University of Missouri)