I'm a simpleton(yr10 schooling) and my vocabulary isnt very good, but I'll try to project what I've "imagined" is outside the universe.

With the big bang theory in-mind, I believe there are layers and layers, each layer containing a subatomic 'independant' particle. self sustained and always moving towards the gavitational pull of our universe. At the end of each layer the 2 particles combine and a reaction occurs(this cycle continues gaining more particles until it becomes visible matter). and I've come to think that outside these layers is pure white/energy (for some reason).

but yeah, its just an un-educated opinion. no flaming please