During the history of the universe, what important event occurred about 0.001 seconds after the big bang?

"Most matter in the early universe was annihilated by antimatter" is the one important event that occurred about 0.001 seconds after the big bang, during the history of the universe. It is considered that big bang is the reason behind the expansion of the universe. I hope the answer has come to your help.

C.about 10% i think