In the Department of Materials Science and Engineering at UCLA, three courses on kinetic processes in materials are being taught at the moment. The first course is MSE 131 on "Diffusion and Diffusion Related Phase Transformations," which is for upper undergraduate students. The textbook is "Phase Transformations in Metals and Alloys," 2nd edition, by D. A. Porter and K. E. Easterling, published by Chapman and Hall, London, 1992. The second course is MSE 223 on "Thin Film Materials Science," which is for first year graduate students. The textbooks are "Electronic Thin Film Science," by K. N. Tu, J. W. Mayer, and L. C. Feldman, published by Macmillan, New York, 1993, and "Electronic Thin Film Reliability," by K. N. Tu, published by Cambridge University Press, UK, 2011. The third course is MSE 201 on "Principle of Materials Science: Solid State Reactions," which is a mandatory course for Ph.D. students. It had been taught by Prof. Alan Ardell until his retirement in 2008. There is no textbook for this course, except the lecture notes by Prof. Ardell. One of the reasons that this book is written is to serve as the textbook for this course in the future. This book can also be used as a textbook for a kinetics course in the Department of Physics at Cherkasy National University, Cherkasy, Ukraine. Roughly speaking, MSE 131 covers mainly kinetics in bulk materials, MSE 223 emphasizes kinetics in thin films, and MSE 201 will focus on kinetics in nanoscale materials. It is worthwhile mentioning that kinetics in nanoscale materials is not completely new or very different from those in bulk and thin films. Actually, a strong link among them can be found, which is shown in this book. An example is the lower melting point of nanosize particles. In morphological instability of the solidification of bulk melt, the lower melting point of the tip of dendrite has been analyzed in detail.