A hyper-contractive inequality for an operator T states that where q > p > 1 for all functions f. Hyper contractive inequalities play a crucial role in analysis in general and indiscrete Fourier analysis in particular. A reverse hyper-contractive inequality for the operator T states that for q < p < 1 (q and p can be negative) and all strictly positive functions f. The first reverse hyper-contractive inequalities were proved by Borell more than 2 decades ago. While these inequalities may look obscure, they have been used for the solution of a number of problems in the last decade. I will survey applications of the inequalities and discuss new results relating reverse hyper-contractive inequalities to hyper-contractive, Log-Sobolev and Poincare inequalities as well as some new applications. This is a joint work with K. Oleszkiewicz (Warsaw) and A. Sen (Cambridge).