M A R L O Y A R L O

Your brain is built of cells called neurons and glia—hundreds of billions of them. Each one of these cells is as complicated as a city. And each one contains the entire human genome and traffics billions of molecules in intricate economies. Each cell sends electrical pulses to other cells, up to hundreds of times per second. If you represented each of these trillions and trillions of pulses in your brain by a single photon of light, the combined output would be blinding.

The cells are connected to one another in a network of such staggering complexity that it bankrupts human language and necessitates new strains of mathematics. A typical neuron makes about ten thousand connections to neighboring neurons. Given the billions of neurons, this means there are as many connections in a single cubic centimeter of brain tissue as there are stars in the Milky Way galaxy.

The three-pound organ in your skull—with its pink consistency of Jell-o—is an alien kind of computational material. It is composed of miniaturized, self-configuring parts, and it vastly outstrips anything we’ve dreamt of building. So if you ever feel lazy or dull, take heart: you’re the busiest, brightest thing on the planet.