Neurochemistry is the study of chemicals and how they work in the brain. We have tiny cells in our brain called neurons, and these neurons need a special type of fuel, or energy, to do their job. That energy comes from chemicals called neurotransmitters. Neurochemists study how these chemicals move around the brain and how they interact with one another. They also look at how different drugs and illnesses can affect how these chemicals act in the brain, which can affect how we think, feel, and behave.