There was this big explosion and when spacetime expanded enough to let all the energy cool down, various subatomic phenomena began to take shape. As it cooled further those subatomic waveforms bound together to create many types of particles, but as we don't yet understand much about any of the others, let's focus on protons, neutrons, electrons, and photons. Cooling further, these grouped together and formed the most complex waveform yet. A single hydrogen atom. Cooling further, these atoms bind into elemental hydrogen. Otherwise structureless clouds of hydrogen gas fill the universe.
Cue gravity. Let's undo the cooling resulting from the expansion of space. Let's bring localized pockets of matter together and "increase" their energy. As those clouds compact the pressure at the center of gravity rises ever more dramatically with mass. Eventually this boring world of hydrogen gas surprises us with even more structure. Hydrogen fuses to create helium and electromagnetic waves (photons). But helium atoms don't link like hydrogen does. Huh. As the pressure increases, more heat is transferred to the core and more and more fusion happens. With enough mass, a star ignites. That structureless cloud of gas begins to take on a very complex shape. As time goes on, more and more layers are created until the star attains critical density and can no longer justify nuclear fusion. A lot of the time this means the core was iron. So yeah the star explodes and the chaotic event causes even heavier elements to form. Now we can start doing some real chemistry, trying to figure out how all these different atoms link up.
Cue, again, gravity. That cloud of elements again pulls together, but this time with very different results. For the first time in the billions of years the universe has existed, we have solid matter instead of gas. A hydrogen ball re-forms at the center of the solar system, sometimes igniting into a star again, and we get various types of second order and even third order satellites - planets and moons, respectively. As this point there is so much structure in the universe that we need to form sub-disciplines. As you increase gravity, and therefore pressure, you eventually get a distinct third phase of matter: Liquids.
I'm not much of a chemist, so I don't know exactly how mind boggling the possibilities are, but they're quickly approaching "inconceivably" as far as I can tell. There is one structure that I think I have a fairly good grasp of though. We'll call them the "organic elements." On Earth, at least, they tend to 1.) form extremely complex molecules naturally, and 2.) react quickly. If the various crystalline forms don't capture your interests, then perhaps an amorphous blob will. You can poke it and split into into smaller bubbles. It's so flexible and strange. By far, I think, the absolute most complex structure ever conceived. It'd be hard for me to imagine anything more complex could possibly arise.
Well guess what? It turns out chemistry has a near-infinite complexity. The number of ways you can construct molecules and the ways they interact is absolutely mind-boggling. With the organics alone you can form some massive molecules composed of long chains of atoms. Acids and sugars and proteins. As it turns out, you can practically program the formation of these things. And, as it happens, there are naturally occurring programs. But not all programs are equal. Some do interesting things and others do a few things and then go inert. You could say they "halt," or, if you prefer, "die."
So the interesting organic reactions continue to occur, cyclically. But it's not a perfect process. Sometimes an atom gets hit by one of the incomprehensibly numerous photons the sun pours out and gets excited out of place and screws up the process. Call it a bug, call it a death, call it failure, but every now and then, these "mutations" don't screw things up. Occasionally, and very rarely, they change the program in a novel way. While the possibilities are endless, the reactions cannot happen without some kind of "fuel." Whether it be some kind of "burning" process that turns O2 and I don't even know into CO2 or some kind of "photosynthesis" that does the exact opposite, the only life that can flourish is the one that has fuel.
Over billions of years, life actually turns out to have the capacity to alter the entire chemical face of the planet. At this point life is so prolific and full of a variety of mutations that even though 99% of them die now that their fuel is exhausted, that 1% goes on to re-proliferate and evolve. Ecosystems arise and these single cells begin to work together. As it turns out, teamwork is awesome for accomplishing goals. Eventually they work so well together that an entire clump of cells acts as an organism unto itself. Of all the unfathomably infinite realms of possibility, that such a structure would arise naturally is beyond my wildest imagination.
It gets worse. Cells begin to specialize. More and more complex multicellular organisms arise. Eventually, and I have no idea how, but at this point I see now reason to question that such a thing is possible, a very strange type of cell manages to find its program occur naturally. A neuron. As a neuron does little by itself, it could never have arisen in the single-celled world. But when you join these cells together, something absolutely remarkable happens. Something so strange, so complex, so incomprehensible, that I find it logically impossible to explain. Thought. Consciousness. Awareness. Decision. Learning. The uncanny ability to alter chemical reactions at whim. No longer are we mere chemical reactions in a vast universe.
Two main types of thinking organisms arise. Predators and prey. Or, as I like to call them, hunters and herds. In the early days, hunters tend to be solitary. Looking out for themselves. Once again, teamwork comes into play. Herding animals further unify and develop a sense of community. Let's call them social creatures. Eventually hunters learn to form packs too, blurring the lines I've attempted to draw in the universe. Over the eons many species come and go as the universe sends chaotic event after chaotic event towards the planets, changing the environment temporarily and forcing life to alter itself in order to flourish more effectively than other lifeforms competing for the same fuel. Apex predators tend to take it the hardest when this happens.
One such social creature finds itself in quite a different environment after one such event. Normally this family of species live in forests. Forests? Oh yeah they're a type of plant. Plants have been around for billions of years now. In fact they're older than the neuron. Well the point is, their environment changed dramatically. For survival's sake, their brains managed to evolve an entirely new way of thinking. Let's call it... Abstract. Let me tell you about intelligence. Intelligence is great. It allows you to make decisions in entirely new ways. Cause and effect are no longer something your neural network calculates and calibrates itself to, but they are coherent concepts in and of themselves. You can reshape your environment in ways you would literally have not thought possible otherwise. Over the years you can reach a point at which your entire world is artificial. No matter where you look, just about everything you see was fabricated at the hands of intelligence.
We're reaching, or have already reached, a point at which we can create entire ecosystems. We can alter the landscape and change anything as we see fit. With time and effort, I'm not sure there is anything we are incapable of. The biggest challenge posed to intelligence comes from that of a competing intelligence. But what about teamwork? What happens when we work together? What happens when our entire civilization, ecosystem, our entire world, unify? What structure might form at such an already unfathomably inordinate level of structural complexity?
Of all the possible answers, that we aren't part of a much larger structure yet to be realized is completely out of line with everything the universe has ever done.