I've always been amazed by anatomy & biology. Life is mysterious, & any explanations we may try to formulate cannot penetrate that essential Mystery.
Science is the ongoing investigation of this infinite Mystery, which gives rise to endless additional mysteries! Scientific understanding and technology (especially 3D digital imaging) allow us to explore aspects of reality that were previously inaccessible, or even unimaginable.
The brain & nervous system is especially interesting, because it it the source of our conscious experience. The video below that I saw on National Geographic is a specific look at the synapse of a neuron, or brain cell. It is from a scientific paper that maps the proteins in these synaptic connection points on the ends of each cell, that allow chemical messages to be sent through the neural network.
click to enlarge
The mind-boggling fact is that all this complexity is packed into a single synaptic area, on a single neuron. There are billions of these cells working together at near-instant speeds to maintain our biological functions and to create the holographic sensorium in our heads called "consciousness".
As much as I love to understand and learn about the world & the universe, looking deeply into these infinitely complex features is enough to melt your brain.