The chapters collected in this Cambridge Companion together demonstrate a few things about the law of international organizations – and law generally perhaps – that may not always be realized. A first point to note is that international organizations are active in nigh-on all walks of life, as these chapters suggest. There are few human activities with which international organizations have no point of contact. Whether it concerns energy provision or the movement of persons across the globe; whether it concerns disarmament or financial stability or the governance of resource extraction, international organizations are often involved in one way or another. And even in those policy domains where there is no single overarching international organization (most conspicuously perhaps the heavily fragmented domain of environmental protection), there are nonetheless entities active which may not generally be considered international organizations (largely because their founding fathers shy away from using that label), but which are remarkably similar to international organizations in all but name.