"With data from satellites like COBE, WMAP, and Planck, we’ve tested all four, and only inflation (and not the non-inflationary hot Big Bang) yields predictions that are in line with what we’ve observed. But this means that the Big Bang wasn’t the very beginning of everything; it was only the beginning of the Universe as we’re familiar with it. Prior to the hot Big Bang, there was a state known as cosmic inflation, that eventually ended and gave rise to the hot Big Bang, and we can observe the imprints of cosmic inflation on the Universe today."
See the comments at the original post in "How Physics Erases The Beginning Of The Universe"