  This is a brief review of liquid scintillators, an important technology for
detection of ionizing radiation. We will first review the basic mechanisms of
light production in most organic liquid scintillators. For most practical
detector applications, the scintillators need to be optimized for choices of
photosensors and compatibility with optical windows. A summary of important
past experimental projects with liquid scintillators is provided. We will
complete the review with a list of modern practices, particularly of metal
doping, and development of water based hybrid materials that allow simultaneous
detection of Cherenkov and scintillation light.
