In the 1940s, researchers Irvine Page, Maurice Rapport, Arda Green and Betty Twarog made pioneering discoveries that transformed modern neuroscience. While investigating hypertension at Cleveland Clinic, Page, Rapport and Green helped identify and isolate serotonin (5-hydroxy-tryptamine). Twarog later demonstrated its presence in the mammalian brain, establishing serotonin as a neurotransmitter. Together, their breakthroughs opened the door to understanding serotonin’s essential roles in regulating mood, appetite, digestion, healing and numerous physiological processes. These discoveries laid the groundwork for decades of scientific progress and reshaped our understanding of the human body and brain.