A Geiger counter is a device used for detecting and measuring ionizing radiation. It is one of the most widely known instruments for radiation detection and is used in various contexts, including environmental monitoring, medical applications, and in the field of toxicology. The Geiger counter is named after Hans Geiger, who, along with Walther Müller, developed the Geiger-Müller tube in 1928. This tube is the core component of the device.