The field of matter transport is central to understanding the processing of materials and their subsequent mechanical properties. While thermodynamics determines the final state of a material system, it is the kinetics of mass transport that governs how it gets there. This book gives a solid grounding in the principles of matter transport and their application to a range of engineering problems. The author develops a unified treatment of mass transport applicable to both solids and liquids. Traditionally matter transport in fluids is considered as an extension of heat transfer and can appear to have little relationship to diffusion in solids. This unified approach clearly makes the connection between these important fields. This book is aimed at advanced undergraduate and beginning graduate students of materials science and engineering and related disciplines. It contains numerous worked examples and unsolved problems. The material can be covered in a one semester course.