On October the 6th the Royal Swedish Academy of Sciences announced that Taakaki Kajita and Art McDonald had been awarded the 2015 Nobel Prize for Physics. These physicists were honoured for their scientific leadership of two collaborations – Super-Kamiokande and the Sudbury Neutrino Observatory – that had shown categorically that neutrinos can change from one type to another, and back again, as they propagate. The corollary of the observation of these oscillations is that neutrinos are massive. The talk will introduce the particle physics of neutrinos, along with a little history, before describing the groundbreaking measurements of the two experiments. The talk will conclude with a brief look at how the further study of neutrinos may elucidate some of the unresolved puzzles in particle physics.