Chapter 2 explains the basics of electrophysiology. The starting point is electrical phenomena and processes at membranes, which are explained in a generally understandable way. Building on this, the main methods of electrophysiology are introduced and compared, from the patch clamp technique to electroencephalography (EEG) in humans. It also highlights the advantages and limitations of each method, for example by comparing patch clamp recordings with the use of conventional “sharp” microelectrodes. The most important electrophysiological measurement methods are illustrated with examples.