Being a group member is an integral part of our everyday lives. Groups may take various forms: from small teams to large dynamic crowds, and from deeply symbolic entities to mere labels for social categories. The influences of within-group processes on the individual are numerous and far-reaching, as is the social context in which the group is placed. This diversity of groups is reflected in the variety of theories that researchers have used to help explain behaviour in groups. These theories quite often reflect an underlying evaluation of groups, from mindless and evil to focussed and task-oriented. They also reflect the complexities of the social and political settings within which theories are formed and research is conducted. Most approaches to the study of groups have to come to terms with the complex dynamics within those groups and, at the same time, with the complex interaction between a group and its environment. Our own impression of groups and group membership may be influenced by our preferences for particular models and explanations, but ultimately, what is evident is that while groups can most certainly provide considerable challenges, they can also provide enormous benefits for group members.