A sperm cell, so small that it can’t be seen by the human eye knows how to merge with an egg of equal size.

It doesn’t know anything. It’s development from a precursor cell has made it into something that is capable of one thing only. There’s no decision making, no "if i do this, then the door will unlock" type of thing. Cells that are capable of fertilization follow a specific set of steps that result from the cells developmental path in order to get the ability to gain entry into the oocyte, any deviation results in that sperm cell not being fit enough to fertilize. The funny thing is, it can even try to fertilize an egg of a different species, the result won’t (usually) be viable, but the sperm will still try. There’s no real recognition involved, no decision making.

Also, size-wise, the comparison between the egg and sperm is actually closer to that of the earth and moon. Fun fact!

Then from there, it knows how to form eyes, a heart, a brain, etc.

Development follows the directions of the DNA contained inside the new cell. However DNA by itself is useless. It’s more like a recipe than a computer code because even by reading the intact genetic sequence of an animal, it wouldn’t give us the first idea as to what type of organism would result from the DNA. You can’t just read genetic code and tell what it will do. However, computer code can be read and translated into a working product. DNA is the index card, the template by which the recipe of the development of an organism occurs. So many other factors are necessary to complete development of even one cell. If specific steps don’t occur before other steps then the end product will be off, different in a potentially life threatening. For instance, in cortical development of the brain, neuroblasts actively divide to form two cells: radial cells, the scaffolding of the early cortex and more neuroblasts. Depending on the presence of the signalling molecule Nestin in the dorsal area of the cell during a certain part of cell division, determines whether the daughter cells will start differentiation into other cells like radial glia or stay the same. My point is that cells are only capable of reacting in a certain way towards a specific stimulus that is determined by way of the pathway it took to get there. It’s no more decision making than a roomba going about cleaning up the floors; when you encounter a wall, turn left 15 degrees and start forward again, etc. DNA provides information storage, but unless it’s in a certain developmental context it’s useless.

We have the power to create life from nothing.

Mashing two cells together hardly equates to nothing

What do you think makes us tick? We’re not connected to electrical outlets.

No, we have little symbionts that live in our cells that are inefficient (but vastly more efficient than our own cells) at creating energy. So we’re hooked up to those. These archae-bacteria have their own DNA and divide separately from our own cells. They even have a double plasma membrane! It’s called Endosymbiont Theory.

What makes my heart pump?

The SA node of each side of the heart keeps a steady pulse without higher brain input. The autonomic (unconscious) nervous system by way of the vagus nerve helps regulate the tempo. Pulse originate from the SA node on each side of the heart and propagate through the cardiac cell walls in a wave-like fashion due to ion concentration gradients shifting. Once they reach the ventricles, a delay is initiated so that the ventricles begin contraction shortly after the completion of the atrial contraction.

Why do we all have different fingerprints?

One of the many developmental questions left out there. Could it be genetic? Maybe. Not in the sense that there are certain genes for certain types of fingerprints like you would see in blood typing, but maybe due to concentration gradients of certain developmental trophic factors at a certain stage of epithelial developmental. That’s a hypothesis, nothing more. We’ll know someday though.

Why do we all have different personalities?

Now this is something I can sink my teeth into. It’s all in your head! The brain, and how certain circuits within it communicate with other circuits, are responsible for our personalities. There’s many documented cases where workers have received traumatic brain injuries (pole through the eye socket) and lived. However, after they healed, they had a different personality. We can infer that personality is a direct result of both natural (genetic) and nurtural (environmental) developmental processes from these people who got their brains rearranged. Our genetics and development through early stages of life help lay the foundation of what we are. Then experiences later in life shape us. It’s a mixture of both. Identical twins very rarely share the same personality, yet have (roughly, within a 200 base pair homology) the same genetic makeup. It could have something to do with early development taking a role, but we also have to take a look at the way they experience the world too. There’s too many factors to ever tell how someone is going to turn out, but we can get a handle on certain personality disorders like depression.