Disciplinary power operates at the level of the individual body: it trains, monitors, and produces individual docile subjects one by one. In his lectures at the Collège de France (collected in Discipline and Punish, The History of Sexuality Vol. 1, and later Security, Territory, Population), Foucault traces the emergence of a different and complementary form of power that operates not on the individual body but on the population as a biological entity: birth rates, mortality rates, disease rates, sexual reproduction, public health, immigration. This is biopower.
Foucault identifies a historical shift in the late 18th and 19th centuries: sovereign power was the power of the king to take life or let live (faire mourir ou laisser vivre). Modern biopower inverts this: it is the power to make live or let die (faire vivre ou laisser mourir). The modern state does not just execute or pardon individuals. It manages population, vaccinating, educating, feeding, policing, caring for, and when necessary eliminating threats to the population's vitality. The shift from punishing individuals for crimes against the sovereign to managing populations for their own biological welfare and optimization is, for Foucault, the defining transformation of modern governance.
A striking and disturbing consequence: if modern power operates through the management of life, through the promotion of health, longevity, productivity, and the normalization of biological populations, then what Foucault calls racism is structurally necessary to biopower. If the state's function is to make the population live and flourish, it requires a mechanism for identifying some within the population as threats to the biological vitality of the whole. Racism provides this mechanism: it identifies some biological group as a danger to be eliminated (physically or socially) so that the rest of the population can be made to live more fully. This is not Foucault's personal politics. It is a genealogical observation: that the Nazi state's combination of intense biological care for the German population (health programs, eugenic breeding, elimination of mental illness) and industrial genocide was not an anomaly grafted onto the biopower framework but its logical consequence when combined with virulent racism. The state that most completely implemented the logic of making live killed the most people.
Governmentality is Foucault's related concept for the broader rationalité of modern governance: the art of governing populations not just through coercion or surveillance but through the shaping of the environment, incentives, and norms within which people govern themselves. Neoliberal governmentality, for instance, does not primarily operate through prohibition or surveillance. It operates by constructing subjects who understand themselves as human capital, entrepreneurs of the self, responsible for managing their own health, education, productivity, and risk. The power is not external. It is built into the very subjectivity of the governed.