The Standard Model, that describes extremely well the particles and their interactions, predicts that neutrinos are massless and only interacts via weak interaction. These properties made neutrinos the least interesting particles of the model... until the discovery that they oscillate! This paradigm shifting result implies that neutrinos are massive particles and opens the door to physics beyond the Standard Model - the holy grail of particle physics. It is now clear that neutrinos could hold the key to many great mysteries of physics, such as the imbalance in the Universe between matter and anti-matter, and several current and next generation of experiments are gearing up to provide new answers. Neutrinos are also the only particles of the Standard Model that could be of Majorana nature, a characteristic that would give considerable strength to theories that propose to explain the mass of these elusive particles and that intend to explain the matter-antimatter asymmetry. After reviewing the intriguing properties of neutrinos and presenting the open questions of our field, I will explain how searching for neutrino less double beta decays with Xenon High Pressure Time Projection Chambers (like the NEXT experiment is doing) could give us a unique opportunity to discover a Majorana neutrino. I will also discuss how such discovery would be a revolution for Particle Physics.