Group phenomena have been the focus of many interpretations and analyses through both research experiments and theoretical interpretations. While experimental evidence can produce and conﬁrm the existence of many important aspects of group dynamics, the value of theories, especially where based on extensive observation and insight, is in their contribution to a richer understanding of some of the more complex phenomena evident in groups, and how to handle them. They can also help to illuminate and organise research evidence in a way which extends its meaning beyond the situations from which they were derived. So you will see that we try and weave them together. No doubt you will do your own testing and weaving too.