One Synapse
A synapse is…
… the space between two cells (neurons) where cell communication occurs. That communication can be instigated by a chemical or by an electrical impulse.
What is super cool about this space - it is so tiny it is impossible to see unless you use an electron microscope. In fact, about 2500-5000 synapses can fill the space taken up by the thickness of a single sheet of paper (a single sheet of paper is approximately 100,000 nanometers thick, whereas a synapse is from 20-40 nanometers thick).
AND even though it is not possible to measure the number of synapses in a human brain (not very ethical to take apart a live person’s brain), research on post-mortem brains suggest that a person has approximately 1000-5000 trillion synapses in their brain.
THAT’s a LOT of communication going on.