The early 20th century saw Charles Sherrington describe nociceptors, specialized pain receptors, fundamentally changing the understanding of pain transmission; in 1965, Melzack and Wall introduced the Gate Control Theory, which profoundly influenced modern pain management by recognizing the brain's role in modulating pain; and John Bonica established the first multidisciplinary pain clinic in the U.S. in 1947, pioneering a holistic approach to chronic pain treatment.