We are living in a world of 6 dimensions

The 3 others one are so small that (around nm: 1/1000 of a mm), that we are still not able to see them…How do we know that they exist? Because scientists are studying the origin of/or try to explain the Dark matter in the universe
Dark matter highlights extra dimensions
 Welcome to the fourth dimension. And the fifth, and the sixth. A team of astrophysicists claims to have identified evidence that space is six-dimensional.
http://www.nature.com/news/2005/050829/full/050829-18.html