A class of naturally occurring lipophilic molecules found in humans and all animals. These chemicals interact with the endocannabinoid system, a nervous signalling system found in all animals, which is responsible for maintaining homeostasis in the body. By binding with endocannabinoid receptors, endocannabinoids keep a variety of functions of the body in balance, such as sleep, mood, memory, pain, learning, inflammation, and hunger. Endocannabinoids are distinct from phytocannabinoids, which naturally occur in the cannabis plant.