CP symmetry violation is the reason that the universe appears to be made more of matter than antimatter. Though if I'm not mistaken, the scale of the violation

CP symmetry violation is the reason that the universe appears to be made more of matter than antimatter. Though if I'm not mistaken, the scale of the violations that we have seen, and the violations that must exist in order for the observable universe to be mostly matter aren't in agreement. We don't see enough CP violating processes to explain this asymmetry in the universe. One of the big open problems in Physics.