At the beginning of the Big Bang, matter and anti-matter were produced in equal amounts. A small imbalance of 1E-9 in the matter to anti-matter ratio at primordial times caused by the mysterious CP violation would be enough to explain the evolution of the Universe after 99.9999999% of the matter and anti-matter would have annihilated to form photons, which we observed as the 2.7 K cosmic microwave background radiation today.