If you were to open up this engine and look inside, you would find (if you had a microscope) a vast web of microscopic-size wires thoroughly connected to each other, and packed densely inside a space about the size of a football. These are your brain neurons and you have about 100 billion of them that form over 1,000 trillion connections. Each neuron has as many as 15,000 connections to other neurons. How vast is this web of wires? Well, if you could remove your 100 billion neurons and line them up one to another, the line would stretch over 600 miles. How many is 1,000 trillion of anything? Enough that if you were to count them 1 per second, it would take you 3,171 years.