[en] We live in a four dimensional world. But the idea of unification of fundamental interactions lead us to higher dimensional theories. Recently a new theory with extra dimensions has emerged where only gravity propagates in the extra dimension and all other interactions are confined to only four dimensions. This theory gives us many new hopes. In earlier theories unification of strong, weak and the electromagnetic forces was possible at around 10¹⁶ GeV in a grand unified theory (GUT) and it could get unified with gravity at around the Planck scale of 10¹⁹ GeV. With this new idea it is possible to bring down all unification scales within the reach of the new generation accelerators, i.e., around 10⁴ GeV. (author)