This chapter is part of a book that aims to map out the emerging field of “biosecurity interventions.” The term biosecurity is used to refer to the various technical and political interventions – efforts to “secure health” – that have been formulated in response to new or newly perceived pathogenic threats. In examining these interventions, the chapters do not focus on the character of health threats per se, or on the social factors that exacerbate disease risk, but rather on the forms of expertise and the knowledge practices through which disease threats are understood and managed. This particular chapter considers containment, and politically modified organisms.