Book excerpt: This book presents synthesis, characterization, and applications of macroporous, mesoporous, nanoporous, hierarchical porous, porous metals, and porous ceramics. Special emphasis is given to the preparation of porous activated carbon materials and porous ionic liquid-derived materials for CO2 emissions mitigation. Additionally, a chapter includes the physical and mathematical modeling in porous media. Many analytical techniques for characterization are discussed in this book. Also, the biomedical and industrial applications of porous materials in adsorption, catalysis, biosensors, drug delivery, nanotechnology are described. The content helps solving fundamental and applied problems in porous materials with length scales varying from macro- to nano-level.