Some animals, like earthworms, snails, and spiders, have nerves but not actual brains.

A one-year-old child's brain weighs about 2 pounds (950 g), ten times the weight of a dog's brain.

The primate cortex is so large that it has to be folded to fit inside the skull. That's why the surface of the brain is wrinkly.

The nervous system runs on electricity, but the levels are low. Brain signals involve less than one-tenth the voltage of an ordinary flashlight battery.