Since I was a boy, the night sky has always fascinated me greatly, with all its stars and the Milky Way—things that, back then, could still be observed clearly without the current light pollution. The sky has fascinated humanity since its beginnings, and over the centuries, the interpretations of everything seen in it have evolved, eventually leading to our current understanding of the Universe. One of the many gaps in our knowledge of the sky above us concerns the mechanisms that power the Sun and stars. Direct investigation of these processes is impossible with man-made instruments due to the extreme temperatures of these celestial bodies. Fortunately, an ideal “probe” for understanding what happens within them is an elementary particle: the neutrino.