  In 1956 Reines & Cowan discovered the neutrino using a liquid scintillator
detector. The neutrinos interacted with the scintillator, producing light that
propagated across transparent volumes to surrounding photo-sensors. This
approach has remained one of the most widespread and successful neutrino
detection technologies used since. This article introduces a concept that
breaks with the conventional paradigm of transparency by confining and
collecting light near its creation point with an opaque scintillator and a
dense array of optical fibres. This technique, called LiquidO, can provide
high-resolution imaging to enable efficient identification of individual
particles event-by-event. A natural affinity for adding dopants at high
concentrations is provided by the use of an opaque medium. With these and other
capabilities, the potential of our detector concept to unlock opportunities in
neutrino physics is presented here, alongside the results of the first
experimental validation.
