To find out the origin of matter in our universe is one of the great goals of physics. Whether there are particles which are at the same time their own antiparticles is a central question. For neutrinos, such a conjecture has existed for almost 90 years. At the Gran Sasso underground laboratory in Italy, the LEGEND experiment should finally provide clarity. Dr. Michael Willers from the Technical University of Munich reports on the large-scale international project.