TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The metal-containing reagent comprises a main group element, a transition metal element, a lanthanide element, an actinide element, and/or a rare earth element.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The aerogel and precursor aerogel monolith comprise a silica-based aerogel, a main group metal oxide-based aerogel, a carbonaceous aerogel, a resorcinol-formaldehyde based aerogel, a transition metal oxide-based aerogel, or a mixed metal oxide-based aerogel. The reagent comprises halide, hydride, amine, alkoxide, alkyl, alkenyl, alkynyl, vinyl, and/or aryl, which has a functional group that cannot react with uncondensed Si-OH to form Si-O-M bonds or a bridging group. The silane reagent comprises silane, methyl silane, methylchloro silane, disilane, dimethylsilane, tetrachloro silane, tricholorosilane, methyltrichlorosilane, ethylenetrichloro silane, di(trichlorosilane), dimethyldichloro silane, trimethoxy silane, triethoxy silane, tetramethoxy silane, methyl di(trichloro silane), ethyl di(trichloro silane), acetylene di(trichloro silane), ethylene di(trichloro silane), or hexamethyl disilazane. Preferred Condition: The reagent diffuses substantially throughout the monolith without substantially unchanging the transparency of the monolith. The aerogel is exposed to reagent for a period of about 6-48 hours. It has a density of 30-290 mg/cc prior to the exposure to the reagent. EXAMPLE - Five aerogel monoliths having density of 290 mg/cc and a respective weight of 0.14 g, 0.79 g, 0.79 g, 0.797g, and 0.810g were prepared. Each one was placed into a vessel and exposed to hexamethyldisilazane at room temperature under a static vacuum (500 mtorr) and atmospheric pressure. After a reaction time of about 48 hours, each monolith was removed from the reaction vessel and weighed to determine the amount of reaction. The monolith weighed 1.04g, 1.0106g, 1.10g, 1.028g, and 1.028g, respectively. No substantial change in the optical transparency of the monoliths appeared.