This book gives a unique overview of principles associated with the characterization of solids with regard to their surface area, pore size and density. The book covers methods based on Gas Adsorption (Physi- and Chemisorption), Mercury Porosimetry and Pycnometry. Not only are the theoretical and experimental basics of these techniques described, but also the most recent developments, particularly in light of the tremendous progress made in recent years in Materials Science and Nanotechnology. The application of classical theories and methods for pore size analysis are discussed in contrast with the most advanced microscopic theories based on statistical mechanics (e.g. Density Functional Theory and Molecular Simulation). The book will appeal both to students and to scientists in industry who are in need of accurate and comprehensive pore and surface area characterization of their materials.