This chapter focuses on time-resolved studies of nanostructure development in sol-gel liquids, that is, diluted sols, wet gels, and drying thin films. The most commonly investigated classes of sol-gel materials are silica, organically modified silica, template-directed mesostructured silica, titania and titania-based materials, zirconia and zirconia-based materials, and few others. After a brief overview of small-angle X-ray scattering (SAXS) theory and some experimental details, the chapter discusses separately each of these classes of sol-gel materials. Nearly all time-resolved SAXS studies on silica have been carried out starting with alkoxysilanes. The chapter discusses studies of systems with a single precursor under acidic and basic conditions, respectively, and reviews combinations of alkoxysilanes with other metal precursors and mixed organic–inorganic systems.