The structure and action of the neurotransmitter serotonin's action within the brain and body were examined. The affect on mood and "happiness" was discussed. The structure of some common serotonin reuptake inhibitors was looked at in relation to how they would block the effect of serotonin reuptake and allow the action of the neurotransmitter to be prolonged. A brief explanation of the chemistry of the molecule, looking at its ring structure, and comparing it to the inhibitor blockers gave a good picture of how the drug might work.