The use of the animal in medical research is deeply embedded within scientific culture, so much so that in spite of the European Union Directive (2010/63/EU) on the protection of animals, linked to the “3Rs” principle of replacement, reduction, and refinement, the recorded use of animals continues to increase. This essay explores the background to the utilization of the animal in experimentation. Using ethnographic data gathered in stem cell laboratories, the author explores attitudes toward the use of alternatives, specifically what is termed “waste” human tissue. A contrast is drawn between the refined framework surrounding the use of the “standardized” animal model and what appears to be the more ad hoc system for human tissue. At a time when the UK government is committed to reducing the use of animals in scientific procedures, it can be concluded that mundane practices, concepts, and values provoke resistance to the use of an alternative material.