Truly ancient history is astounding to ponder. You can think about how things were in your grandparent's day, and very little has changed. You can go back 5000 years in human history and the only real difference is the knowledge and technology. Hell we could go back 100 million years and it might seem like strolling through a field, except you have to watch out for dinosaurs instead of bears. But go back a couple billion years and we would probably have no chance of survival.
Now take that on the cosmic scale, the differences in the early universe when it was less than a billion years old would be unrecognizable from anything we know. A cosmic hydrogen fog??? That sounds like an atmosphere, something that a space-dwelling creature from a sci-fi novel could develop in. And given the immense stretch of time since then, could such a creature evolve to survive in the rarity of matter between stars today? When you consider just how long of a period several billion years is, it really seems like anything could be possible.