The discovery of non-zero neutrino mass is our first direct evidence of physics beyond the Standard Model. Neutrinoless double beta decay (0νββ) is a proposed form of radioactive decay that remains undetected yet is crucial for understanding the fundamental properties of neutrinos. The process is only possible if neutrino is its own anti-particle. A discovery of 0νββ will be a direct observation of lepton number violation, shed light on the dominance of matter over antimatter in the Universe, and provide a probe into the nature of neutrino mass. In this talk, I will describe a new generation of experiments designed to significantly push the detection sensitivity to 0νββ beyond the current half-life limits, focusing on the nEXO experiment. nEXO experiment searches for 0νββ of Xe-136 using 5 tonnes of enriched liquid xenon at > 1028 year half-life sensitivity, two orders of magnitude above current experiment limits. In this talk I will present the design and R&D efforts to achieve this exquisite sensitivity.