Two of the biggest open questions in the Standard Model of Particle Physics are whether the neutrino is its own antiparticle – a Majorana particle – and whether Peccei-Quinn symmetry, with its associated axion, provides a solution to the strong CP problem. Resolving these questions would not only extend our understanding to the GUT scale but also address the origins of the universe’s matter-antimatter asymmetry and the nature of dark matter. My group approaches these problems through searches for neutrinoless double-beta decay and axion dark matter, with a particular focus on cryogenic detectors. In this talk, I will review the physics that connects these efforts, the current status of the fields, and our work advancing next-generation cryogenic detectors, including the integration of quantum sensing technologies.