This essay investigates milk as a material with various meanings and compositions in different historical and cultural contexts. I bring together research from the several disciplinary fields where “milk studies” has already begun: food studies, postcolonial studies, animal studies, feminist studies, environmental justice, animal science, and biology. Using these perspectives, I investigate milk by addressing topics such as breastfeeding/nursing across race, class, and species in US history; US dairy industry production practices, economics, and the biological and behavioral experiences of lactating cows; India’s Operation Flood (also called the “White Revolution”) and its devastating effects on mothers and children, cows and calves, rural poor and small dairy farmers; and the US Dairy Council’s eurocentric and nutritionally unsupported ads promoting milk as the “perfect food.” Influenced by feminist philosophers of science, postcolonial ecofeminisms, and the new material feminisms, I examine the animal sciences research on lactation, oxytocin, and maternal behaviors by juxtaposing them with the biosciences studies of lactating human mothers, hormones, and behaviors: read together, these scientific studies show few differences across lactating mothers of diverse species, yet their findings are interpreted in ways that reaffirm the cultural assumptions of the researchers’ various disciplines. In sum, I argue for bringing together these various disciplinary approaches in a new critical framework, one that is sufficiently inclusive and capable of describing the complex cultural assumptions and material practices articulated through the uses of milk across nations, genders, races, species, and environments.