What is your most epic worldbuilding revelation thus far?

Mine is that, after a lot of thought, my universe's Milky Way looks like exactly what it is, a spiral galaxy with a bunch of stars with various levels of gas, planets, and other stuff. The reason is that my universe's "big bang" was basically exactly what it is, a cosmic explosion that caused a massive scatter of particles across a large area. It's that large area that can be called the universe. My universe has no infinite expansion with the Big Bang at the center, it's just a giant galaxy in an absolute void as far as nearby observers can see.