This paper lays the groundwork for a first-of-its-kind multi-sited ethnographic study in the STS subfield of medical anthropology on rejuvenation cellular therapy and "stem cell" clinics in two sites: Switzerland and the Ukraine. By weaving together intricate sociotechnical histories and their esoteric roots, the in-depth case studies create new space for the discussion of boundary making in the social construction of scientific disciplines, as well as tensions, translations, and conflation in the divide between human and nonhuman tissue subjects. It asks the question: How, why, and at what cost do people opt to try to augment and extend their lifespans with the use of human and/or animal cellular material? (A look at the history, present, and potential futures)