Chronic pain has a profound cumulative impact on our nation, affecting over 100 million Americans a day, at a cost of $500 billion in health care and lost productivity each year. Pain is a complex, subjective experience that displays considerable variability compared to other sensory modalities. For instance, in some people intense noxious stimuli are not reported as painful, whereas others can experience excruciating pain from light touching of the skin. Some people are highly sensitive to pain relief from placebo administration, while others are insensitive to even high doses of morphine. Following nerve injury, only a small proportion of people go on to develop neuropathic pain. Our research is focused on uncovering and explaining the sources of variability in these phenomena.