 The observation of the neutrinos from the basic reaction of this chain, proton-proton fusion in deuterium, was achieved for the first time by Borexino in 2014.In 2012 the same collaboration reported detecting low-energy neutrinos for the proton-electron-proton (pep reaction) that produces 1 in 400 deuterium nuclei in the sun.The detector contained 100 metric tons of liquid and saw on average 3 events each day (due to C production) from this relatively uncommon thermonuclear reaction.