Hey,
This is a complicated question that would be debated by many physicists. How to answer this question when we are struggling with the genesis of the universe? Many theories on the origin of the universe have been put forward, but the Bing Bang is probably, or at least to date, the most likely theory. If today the universe is expanding, some astronomers hypothesise that before the Bing Bang the universe already existed but that it was condensing, according to this hypothesis the Bing Bang would correspond to the limit point of compression of the universe.
But if we remain in the traditional theory the Bing Bang is at the origin of all the matter we know, as well as light. Before the Bing Bang, in other words before the universe, there was NOTHING.