in Sex, Gender and Pain at the International Association for the Study of Pain. His team showed in 2015 that male and female mice were employing wholly different immune cells—microglia and T cells, respectively—in the spinal cord to process chronic pain. This finding was immediately influential within the scientific community and widely covered in the media. It was voted the #1 discovery of 2015 by Quebec Science magazine, inspired an editorial in the New York Times, was chosen as one of 10 milestones in pain research from 2000 BC to the present by Nature, and was cited by funding agencies in Canada and the United States in support of new Sex as a Biological Variable policies. Other notable sex difference findings from his group include a meta-analysis showing that women are more sensitive to pain than men; morphine analgesia, stress-induced analgesia, and opioid-induced hyperalgesia are mediated by different neurochemical receptors in the two sexes (NMDA receptors and V1AR receptors in males, and MC1Rs in females) in male and female mice and humans; male and female mice have equivalent variability in pain sensitivity; pain variability is due to different genes in both sexes; female mice are more sensitive to itch than male mice; pain reduces sexual desire in male but not female mice; sex differences in morphine analgesia may be mediated by T cells; pain affects dominance hierarchy in male but not female mice; and, male but not female mice and humans display classically conditioned pain hypersensitivity. Development of rodent "Grimace scale" For the past century, the measurement of pain in rodent biomedical research was considered complicated and imprecise, and many researchers suggested there is a mismatch between human clinical pain symptoms and established procedures in rodents. Based on the human Neonatal Facial Coding Scale, which is itself based on the Facial Action Coding System, Mogil and colleagues developed the Mouse Grimace Scale and the Rat Grimace Scale. The original findings were highly cited, widely covered in the scientific press, and Mogil was awarded the Bennet Cohen Award from the International Council for Laboratory Animal Science and the SGV Award from the Swiss Laboratory Animal Science Association for the finding. Grimace scales are now routinely used in institutional veterinary settings for the determination of post-operative pain in animals, and have been developed for 10 species: mice, rats, rabbits, cats, horses, cows, pigs, sheep, ferret, and seal. Mogil's laboratory has made a