The law of international organizations is a field of study full of themes with variations. With respect to a number of key chapters in this field, such as the legal status of international organizations, their institutional structure, powers, decision-making and decisions, sanctions, fundamental principles exist or are being developed. These principles or themes have a large number of variations in the rules and practice of individual organizations. Like in music, the variations in themselves may be interesting as such, but they can only be fully appreciated by not losing sight of the theme. Like in music, the themes in themselves may be interesting as such, but they can only be fully appreciated by also listening carefully to the multicoloured variations. This contribution is devoted to a central theme of the law of international organizations: the relationship between an international organization and its members. Already in the early days of existence of international organizations, this topic has given rise to numerous questions. Many of these have now been answered, but sometimes resurface in contemporary variations. In addition there are new questions. It is useful to first explore briefly the meaning of the word "members". The English word "member" and the French "membre" are both derived from the Latin word "membrum", which means "part of the body". This meaning is important because it indicates clearly that members are part of a whole – a fact which takes us straight to one of the core questions addressed in this article. Members of an international organization are not just members, after all – like the members of a bridge club or a gardening club. In most cases, the members of international organizations are states. How then can members of an international organization be members of a whole when in most cases those members are sovereign states, even if the concept of sovereignty of states is no longer as absolute at it used to be? This is one of the major questions within the field of the law of international organizations. In order to examine this question, this contribution is divided into two parts. Section I will concentrate on the role of members vis-à-vis international organizations. In Section II the focus will shift to the whole of which the members are part; this Section will briefly look at some of the questions involved in giving a certain amount of autonomy to this whole.