In 1988, Devane et al. reported the existence of cannabinoid-binding sites in the human brain. This CB1 receptor was cloned in 1990 and identified as part of the family of G protein-coupled receptors. A second cannabinoid receptor, CB2, was discovered in 1993 (Munro et al. 1993). We now know these two cannabinoid receptors exist in all chordates and evolved hundreds of millions of years ago (Pertwee et al. 2010). The presence of these receptors implies that humans (and other chordates) produce their own compounds that bind to these receptors. Two such endogenous or endocannabinoids have been discovered and characterized. There is currently an ongoing effort to understand which cannabinoids affect which neuropathways; this involves a tremendous team of professionals from multiple disciplines in science.