In this middle there is a tower where a guard can be placed to observe the prisoners. Since the prisoners will never be able to know whether they are being watched or not at a given moment, they will internalize the disciplinary power and regulate their own behavior (as if they were constantly being watched). Foucault says this construction (1) creates an individuality by separating prisoners from each other in the physical room, (2) since the prisoners cannot know if they are being watched at any given moment, they internalize the disciplinary power and regulate their own behavior as if they were always watched, (3) the surveillance makes it possible to create extensive documentation about each prisoner and their behavior. According to Foucault the panopticon has been used as a model also for other disciplinary institutions, such as mental asylums in the 19th century. Biopower With "biopower" Foucault refers to power over bios (life)—power over populations. Biopower primarily rests on norms which are internalized by people, rather than external force. It encourages, strengthens, controls, observes, optimizes and organize the forces below it. Foucault has sometimes described biopower as separate from disciplinary power, but at other times he has described disciplinary power as an expression of biopower. Biopower can use disciplinary techniques, but in contrast to disciplinary power its target is populations rather than individuals. Biopower studies populations regarding (for example) number of births, life expectancy, public health, housing, migration, crime, which social groups are over-represented in deviations from the norm (regarding health, crime, etc.) and tries to adjust, control or eliminate these norm deviations. One example is the age distribution in a population. Biopower is interested in age distribution to compensate for future (or current) lacks of labor power, retirement homes, etc. Yet another example is sex: because sex is connected to population growth, sex and sexuality have been of great interest to biopower. On a disciplinary level, people who engaged in non-reproductive sexual acts have been treated for psychiatric diagnoses such as "perversion", "frigidity" and "sexual dysfunction". On a biopower-level, the usage of contraceptives has been studied, some social groups have (by various means) been encouraged to have children, while others (such as poor, sick, unmarried women, criminals or people with disabilities) have been discouraged or prevented from having children. In the era of biopower, death has become a scandal and a catastrophe, but despite this biopower has according