Book excerpt: Elementary Processes in Excitations and Reactions on Solid Surfaces explores the fundamental nature of dynamics on solid surfaces. Attempts are made to reveal various aspects of elementary processes in excitations and reactions on solid surfaces by recent theoretical and experimental developments of the subjects such as molecular beams interacting with surfaces, ion beam scattering, laser-induced dynamical processes, electronically induced dynamical processes, and optical properties of solid surfaces. This volume is devided into three parts. Part I is concerned mainly with the rich reaction dynamics on potential-energy surfaces. Part II is devoted to the interplay of excitations. In Part III, new and rapidly developing methods are introduced.