The human body also produces endogenous cannabinoids, called endocannabinoids in contrast to those produced externally in the cannabis plant called phytocannabinoids. These endocannabinoids bind to two different types of receptors, CB1 which are found primarily in the central nervous system, and CB2, located in the peripheral nerves and mainly affecting the autoimmune system.  Science has still to fathom the complete range and functions of the endocannabinoid system, discovered only in 1990 while researching THC. It has been established, however, that it regulates sleep, mood, appetite, memory, reproduction, and fertility.