Hans Berger was a pioneering German psychiatrist and neurologist best known as the inventor of the electroencephalogram (EEG). His groundbreaking work allowed for the recording of electrical activity in the brain, which he famously named 'alpha waves.' Despite initial skepticism from the scientific community, his discovery laid the foundation for modern neuroscience and is now a critical diagnostic tool in medicine. Berger's research fundamentally changed the understanding of brain function and its relationship to psychological states.