With the development of more sophisticated, mostly multi-precursor sol-gel materials, the structure of the building blocks and their mutual arrangement on a nanoscopic scale is getting more and more important, The question how the structure of oxometallate clusters as primary hydrolysis products is influenced by bidentate organic ligands is discussed for a series of methacrylate substituted oxozirconium clusters with different metal : methacrylate ratio, On a larger scale, assembly of the molcular building blocks to form a gel network was investigated for gels prepared by base-catalyzed reaction of Si(OR)(4)/ RSi(OMe)(3) mixtures. When the functional organic group R' has no strongly basic properties, the gel network is formed in two stages. The R'Si= units condense to a gel network formed by the faster reaction of Si(OR)(4). When R' contains a strongly basic substituent such as amino groups, both RSi(OMe)(3) and Si(OR)(4) are involved in the built-up of the gel network, possibly by extensive hydrogen bonding between the amino groups and silanol groups.