What you have to think about is, we had a Universe with a hundred billion galaxies, a hundred billion stars each, at early times, those hundred billion galaxies were squeezed into a region about this big, literally at early times; you had to imagine doing that squeezing without any imperfections, without any little spots where there were a few more atoms than somewhere else, because if there had been, they would've collapsed under the gravitational pull into a huge black hole. 