Abstract
In this lecture the development of arrays of γ-ray detectors is described. The starting point is the reason why we want to study γ-rays emitted in nuclear reactions. An account of how gamma rays interact with matter follows. The characteristics of the γ-ray detectors needed for the study of both exotic nuclei and high spin states are then outlined. The development of γ-rays arrays is followed up to the present introduction of detectors based on gamma-ray tracking. Examples taken from experiment are used throughout.