Nucleation and growth of particles are essential features of the formation of stable and metastable solid phases in a bottom-up approach. These processes are of fundamental importance, bearing considerable relevance to countless processes in nature and industry. Typical examples are the generation of nanoparticles of noble metals, the formation of high performance materials from supersaturated solution of calcium carbonates and phosphates in nature or the development of highly porous materials like metal organic frameworks (MOF) in order to store hydrogen or to act as catalysts. By applying new techniques in time-resolved LS and SAXS, we succeeded to shed light on the mechanism of amorphous CaCO3 formation and are currently investigating the formation of silica nanoparticles and zinc imidazolate frameworks. Development and application of new kinetic models to describe time-resolved scattering data is expected to reveal nucleation and growth mechanisms for the formation of nanoparticles.