The endocannabinoid system (ECS) is comprised of receptors, ligands, and enzymes that create and metabolize those ligands. The receptors are grouped into two main classes, however, many subclasses also exist. The main functions of the ECS are creating homeostasis and facilitating communication among the various body systems. This lecture will begin with a more in-depth look at the receptors and functions of the ECS, and continue with how pain and mood are modulated. We’ll then discuss the complex subject of the ECS’ role in epilepsy. Finally, literature surrounding the use of phytocannabinoids, such as CBD, will be presented.