In recent years, interest in the preparation and characterization of the na-noporous materials has grown due to their distinctive properties and potential applications. Among them, silica aerogel are transparent, highly porous and lightest synthetic solids. Silica aerogels, prepared by sol-gel method followed by supercritical drying, have various extraordinary properties viz. low density ( 20 mg/cm3) and thermal conductivity (0.05 W/mK), low sound velocity ( 100 m/s) and large surface area (> 1500 m2/g). Due to this unique combination of properties, aerogels are considered as a new class solid state porous material having various scientific and technological applications like super insulating transparent fillers in double walled windows, catalytic supports, Cerenkov detectors, filters and containers for capturing of micrometeorites in space. However, economic large-scale industrial production of silica aerogels is hampered by expensive supercritical drying methods. The present book describes the results of detailed studies made on the synthesis and characterization of silica aerogels and related nano-porous materials by various methods and precursors at ambient pressure.