It has often been said that the problem with climate change is its invisibility. People do not mobilize about climate change because they cannot see it; even less can they see CO2 emissions—that is, the most relevant material element causing climate alternations. Although I would argue that for some people climate change is more visible than for others, it remains a global environmental problem not easily felt on the ground. On the other hand, waste appears to be an incumbent presence, almost impossible to avoid; it also seems more localized than global climate change. People mobilize around waste because it stands in front of their eyes and noses. This is how the story has been told so many times. This article instead tells another story, one in which climate activism is rooted in struggles against waste contamination. In Naples, Italy, twenty years of mobilization against toxicity—which, by the way, is much less visible and much more harmful than the urban garbage in the streets—has generated an epistemic community trained to understand the invisible connections linking local problems, global issues, and socioenvironmental inequalities. Their original elaboration of biocide as the theoretical framework explaining the production of toxic communities provided them with an equally original framework to understand climate change and its unequal impacts on people and ecosystems. In moving between waste and climate, local and global, those epistemic communities have not only changed the ways in which climate activism has been conceived but have also changed themselves.