Recent developments in the theoretical and practical problems of porous media physics are reviewed in this volume. The main emphasis is on the interdisciplinary nature of transport phenomena in porous media study. State-of-the-art reviews and descriptions of innovative research in progress are reported. A broad spectrum of problems and techniques related to porous media physics is presented. Fundamental questions currently under investigation provide a unifying theme in this volume, helping the reader to understand the problems and research trends in the field. The first part focuses on general problems and techniques. Phenomenological aspects of averaging techniques, the hierarchy of scales that are involved in real porous media and the related scaling problems of multiphase, multicomponent transport phenomena are examined with the emphasis on providing the basic scientific background for a variety of applications. Sometimes, theory comes very close to applications, and occasionally they diverge. This timely treatise demonstrates that both is now the case in porous media physics. This volume will prove an indispensable reference source for all those interested in resolving discrepancies through innovative research work, and inspiring new advances in the field.