The brain cells you think with are called neurons. They work by collecting information, transforming it, and passing it along. They can connect to sensory cells, like those in your eyes and ears, they can connect to each other, and they can connect to nerves that control muscles.
Altogether, you have about 86 billion neurons. That is a lot. A stack of eighty-six billion dimes would reach a third of the way to the Moon. But that is just the beginning, because each neuron is linked to thousands of others, which gives you more than a hundred trillion connections, more than the number of stars in a thousand galaxies.
All those neurons with all their connections are arranged in a vast, layered network that is constantly adjusting and reorganizing itself to meet the challenge of being you in your world. They are doing that now. That is why you can read these words.
The whole thing weighs about as much as a large cantaloupe, 1.4 kilograms in an adult, and it is about that size and shape too. By the age of ten yours is nearly full size. It runs on about 20 watts, less than an old light bulb, which is a fifth of everything your body burns while resting. In a small child it is closer to half. Signals travel through it at anywhere from walking pace to highway speed, and a thought from eye to hand takes about a third of a second.
Below is a map. Tap a name and the part of the brain that does that lights up, with a sentence about it. Deeper parts turn the brain over so you can see them on the cut. Under the names are ten things your brain does; tap one and watch the signal travel, as slowly as you like or at the speed it really happens.
Made for Curious Woods. The paintings are ours; the regions are placed by eye; the routes are drawn where the anatomy is well known and sketched where it isn't. The times come from the neuroscience literature and are rounded: the eye reaches the switchboard in about 35 ms, the back of the head about 25 ms later, and a simple decision reaches the hand at about a third of a second. The shimmer stands for electrical activity; its pace is a picture, not a measurement. Nothing here scores anyone or leaves the device.