In this paper, I will discuss from a 'Science and Technology Studies' perspective three different modes of caring about the social complexity in biomedical and nanomedical research. Nanomedical research unfolds a variety of issues that generate different concerns, questions, problems, requirements and interests that connect with different systems of action (in vitro, in vivo), different kinds (human, nonhuman) and different scales of action (nano, micro, macro). To adequately address the social complexity, I will discuss three possible modes of caring about social complexity: laboratory experiment and scientific analysis, public expert controversies, and publics. These different modes of caring share an experimental ethos that engages nanomedical issues for which no common solutions are available.