Neuroscience on Metaphors:
Look at neurons from [a human and a fruitfly] under a microscope and they look the same. They have the same electrical properties, many of the same neurotransmitters, the same protein channels that allow ions to flow in and out, as well as a remarkably high number of genes in common. Neurons are the same basic building blocks in both species.
So where’s the difference? It’s numbers — humans have roughly one million neurons for each one in a fly. And out of a human’s 100 billion neurons emerge some pretty remarkable things.