This book is a concise introduction to the experimental technicalities of low and ultralow temperature physics research. The author has made extensive use of diagrams as aids to understanding, and refers the reader to the professional literature at appropriate points in the text. The book begins with an introduction to the thermodynamic principles of refrigeration and thermometry. It covers the properties of fluid 3He/3He mixtures and the most important practical means of achieving low temperatures, including dilution and Pomeranchuk refrigeration and adiabatic nuclear demagnetisation. The basic introduction to the subject will be of value to postgraduate students beginning research in low temperature physics, and to seasoned researchers moving into the field. It could also be used by advanced undergraduates taking low temperature physics courses.