Migmatites are complex, high-grade crystalline rocks that have formed by partial melting. They have been recognised within the crustal rock record across most of geological time, are seen to be developed in various tectonic settings, and can affect a wide range of protoliths. Consequently, migmatites are commonly encountered in the field, where their complexity can confuse and intimidate the geologist. These rocks are particularly common in basement areas of South Australia and are therefore likely to be encountered by geologists working in this state. The aim of this report book is to provide an understanding both of the terminology applied to migmatitic rocks and of the processes that form them, and also to point out their scientific usefulness. To achieve this, the report is divided into three main sections. The first section is conceptual and provides the petrological background knowledge that is necessary to learn in order to understand and describe these rocks. This will include how they form, the parts of a migmatite, and the different types of migmatitic rocks and what they mean. The second part provides some practical mapping guidelines, including what information can be extracted from a migmatite, dating of these rocks, their relationship to mineralisation, and some ideas on how to deal with migmatitic rocks in the field. The final section includes a collection of case studies from South Australia which will give the reader some idea of what information can be extracted from migmatitic rocks. The first part of this review is largely based on the Atlas of Migmatites by E.W. Sawyer (2008), which is an excellent, amply illustrated account of the description and origin of migmatitic rocks. This book also has a very comprehensive background section with a bibliography of the more detailed literature, and is highly recommended.