A view inside the Borexino detector showing its nested nylon vessels, as the inner volume is being filled with 278 tonnes of liquid scintillator. Solar neutrinos are detected through their scattering off electrons in the scintillator: the scattered electrons emit scintillation light that is recorded in phototubes. The photo was taken from a camera mounted on the 14-metre-diameter stainless-steel sphere that surrounds the detector. The camera looks out between several of the cones (in the foreground, and thus seemingly enlarged) that help to direct the light into the phototubes.
Borexino Collaboration