  This is the 10th article in the collection of reviews "Exact results on N=2
supersymmetric gauge theories", ed. J.Teschner. It reviews correspondences
between three-dimensional gauge theories and complex Chern-Simons theory on
suitable three-manifolds. Such correspondences are in many cases deeply related
to the 4d/2d correspondence discussed in this collection. The partition
functions of the three-dimensional gauge theories are calculable by means of
localisation (as discussed in article no. 9 by K. Hosomichi), and the results
are related to the quantum theory obtained by quantisation of Hitchin's moduli
spaces.
