The concept of size-dependent material properties becomes dominant in the materials science community. Understanding the size-dependent properties of materials is the most challenging issue in advanced material science. To a great extent, this is a result of the technological requirements concerning the development of materials with controlled properties, as well as of the recent progress in materials science, nanotechnology, and computational chemistry. The aim of this Special Issue was to discuss the dimensional effects of materials for environmental protection and clean energy production as an innovative approach for the development of innovative materials with improved properties. The Special Issue comprises, but is not limited to, the following three main classes of advanced inorganic materials that form the basis of modern technologies: (1) materials and thin films for environmental protection; (2) materials for clean energy storage; and (3) ceramics/bioceramics and glasses for better living (with applications in optics, molecular electronics, and medicine).