This book provides a compilation of important optical techniques applied to experiments in heat and mass transfer, multiphase flow and combustion. The emphasis of this book is on the application of these techniques to various engineering problems. The contributions are aiming to provide practicing engineers, both in industry and research, with the recent state-of-science in the application of advanced optical measurements. The book is written by selected specialists representing leading experts in this field who present new information for the possibilities of these techniques and give stimulation of new ideas for their application.