Some scientist even propose that for the short time after the Big Bang our universe was 1 dimensional line. They say that transition happens at some point when universe "cools down", 1D -> 2D was expected at 100 TeV energy, 2D -> 3D at 1 TeV, more in the literature: https://phys.org/news/2011-03-physicists-dimensions-universe.html

Thank you for your comment :)