Voice 2: The brain has an outer layer around an inner mass. The outer layer is called the "cortex". The cortex is only a few millimetres thick. But it holds about seventy thousand million brain cells! These cells in our cortex are a grey colour, so together they form our 'grey matter.' This part of the brain stores pieces of information. But the cells in the grey matter need to communicate with each other. This is where 'white matter' comes in. The white matter is the inner part of the brain.

Voice 1: Each brain cell has long extended arms. The cell sends information down one arm called an axon. Think of it like a telephone sending information down a wire. Every cell has one of these axons. The cell also has other arms — called dendrites. These are lines for receiving information. The axons and dendrites extend away from the grey matter on the outside of the brain to the white matter inside. In fact they are the white matter — because axons and dendrites are white in colour. The axons and dendrites permit brain cells to communicate with each other. They can connect, disconnect, and reconnect. Where they meet, an axon and a dendrite form a synapse. A synapse is a kind of meeting point. The axon of one cell passes information to a dendrite of another cell through a synapse.