Biological systems exhibit a wide range of molecular mechanisms and behavioral strategies to ensure their survival under variable conditions. All of these mechanisms tend to be interpreted as regulatory because they contribute to the maintenance of the system’s viability against perturbations by modulating their own basic dynamics. However, despite the widespread appeal to the notion of regulation in biology, be it for explanatory, modeling or defining purposes, the meaning of this notion is left somehow vague and its relationship with akin concepts, such as homeostasis, robustness, feedback or adaptation is hardly stated in clear terms. I will propose an organizational approach to regulation, by focusing on the mechanisms at the basis of responses to perturbations in minimal living systems. In the first place, I will analyze different forms of control in the cell, and how they can be recruited by biological organization to respond to internal or external perturbations. In doing so I will distinguish between two different classes of responses, based respectively on stability and regulatory mechanisms. I will describe the limits of stability as an adaptive response, and I will provide a definition and a basic set of organizational requirement for regulation, by pointing out the differences with similar concepts such as feedback. robustness and homeostasis.