Biopolitics approaches population as a political and scientific problem-space. Contemporary biopolitics operates primarily, although not exclusively, through security mechanisms rather than disciplinary ones. This chapter specifically addresses how populations, particularly childhood populations, are constituted in political and social policy as national and international security concerns. The chapter explores two specific childhood populations. First examined is the growing population of poor children living in a politically aware, but disenfranchised, developing world. Examined next are the children of migrant flows into the United States over the last several decades and how cultural imaginings and governmental technologies have approached this population. These discussions are contextualized in relation to the idea of the United States as a “security state.”