The Common Fund’s Cellular Senescence Network (SenNet) Program was established to comprehensively identify and characterize the differences in senescent cells across the body, across various states of human health, and across the lifespan. SenNet will provide publicly accessible atlases of senescent cells, the differences among them, and the molecules they secrete, using data collected from multiple human and model organism tissues. To identify and characterize these rare cells, SenNet will develop innovative tools and technologies that build upon previous advances in single cell analysis, such as those from the Common Fund’s Human Biomolecular Atlas Program and Single Cell Analysis Program. Lastly, SenNet aims to unite cellular senescence researchers by developing common terms and classifications for senescent cells.