Chapter 2 traces the development of electroencephalography (EEG) from its inception with Richard Caton’s pioneering work in 1875 to its current status as a cornerstone of human neuroimaging. The chapter discusses how EEG captures the electrical signals generated by synchronous activity of pyramidal neurons arranged in open fields perpendicular to the cortical surface. It examines the technical evolution of recording systems, from basic silver-chloride electrodes to modern active electrode arrays with built-in amplification, and explains the standardized 10-20 electrode placement system that enables spatial mapping of brain activity. The chapter addresses the inverse problem that constrains EEG’s spatial resolution while highlighting its exceptional temporal precision for tracking neuronal events in millisecond timescales. Special attention is given to the characteristic oscillatory patterns in different frequency bands (alpha, beta, theta, delta, gamma) and their association with cognitive states ranging from deep sleep to focused attention. The chapter details practical considerations for obtaining clean recordings, including artifact reduction techniques and experimental design. By evaluating EEG’s strengths (temporal precision, direct measurement of neural activity, accessibility) alongside its limitations, the chapter positions EEG as an enduring, versatile tool for both clinical applications and cognitive neuroscience research despite technological advances in other imaging modalities.