A neurotransmitter is a chemical messenger that carries signals between nerve cells in your brain and body. Think of your nervous system as an incredibly complex postal service, where billions of messages need to be delivered every second. Neurotransmitters are the tiny packages that carry those messages across the microscopic gaps between nerve cells.

When you decide to raise your hand in class, neurotransmitters help carry that signal from your brain down through your nerves to the muscles in your arm. When you feel happy, scared, or excited, neurotransmitters are involved in creating those feelings. Different neurotransmitters do different jobs: dopamine is involved in feelings of reward and motivation, serotonin affects mood and sleep, and adrenaline (also called epinephrine) triggers your body's alert response when something startling happens.

Your brain contains trillions of connections between nerve cells, and neurotransmitters are constantly being released, received, and recycled to keep everything running smoothly. Scientists have identified more than 100 different neurotransmitters, each with its own special role in keeping your body and mind working together.