In the classic novel, Frankenstein, Doctor Frankenstein creates a living creature in the hope of cheating death. The monster, as the creature is called, horrifies Doctor Frankenstein, turns against him, and kills several people, causing the doctor to regret his decision to make the monster in the first place. When states establish an international organization (IO), they create an institution with a life of its own on the international stage. Though states can, collectively, control the IO, without unanimity among them the organization can often act on its own. The danger for a state, then, is that its creation, like Frankenstein’s, will become a monster and act contrary to its interests. In contrast to Frankenstein, however, states are conscious of this risk and are able to guard against it. This Article explains that much of the existing landscape of international organizations has been formed by the state response to this “Frankenstein problem.” The effort by states to avoid creating a monster explains, among other things, why there are so many IOs, why they vary so widely in scope, and the manner in which they are permitted (and not permitted) to affect international law and international relations. The Article also identifies the four types of activities that IOs are allowed to undertake and explains how states choose which activities to place within which organizations. More generally, the Article offers a better understand of why and how IOs are designed and their place within the international legal order.