The little grey cells that make up your mind are primarily neurons. You have approximately 100 billion of them in your head!

The typical neuron is connected to thousands of others forming an inconceivably dense signal-processing network. With over a 1,000 trillion connections, or synapses, in your brain, there are more transmission-pathways in your head than there are atoms in the universe. But before you let that go to your head, think about this: the number of synapses peaks in early childhood, so the average three-year-old has ten times as many as the average adult!

Of course, a linear relationship between synaptic-density and cognitive ability has never been scientifically demonstrated. (If you need help with that sentence, ask a toddler).

But measuring brain-power doesn’t have to be tricky: research shows that there is enough electrical power flickering in your neurons to illuminate a flashlight bulb.

Or build one. It just depends how you think about it.

All a single neuron can do is flash a small signal on to its neighbours – and only when enough incoming synapses are active.