Appearance of a solid phase from aqueous solution, known as precipitation, is responsible for the formation of numerous natural materials and technological products. Therefore, the knowledge on mechanisms of elementary processes involved in precipitation should be considered in the areas such as geology, oceanology, biomineralization, medicine, basic chemical and pharmaceutical industries, analytical and materials chemistry in particular. Calcium carbonates are a very suitable model system for investigations of these processes. Owing to their low solubility, a wide range of initial supersaturations can be achieved that direct to different conditions under which a particular process dominates. Calcium carbonates can precipitate in the form of six modifications (polymorphic or hydrated). In the Laboratory for Precipitation Processes, systematic investigations of the conditions for formation, crystal growth and transformation of amorphous calcium carbonate, calcium carbonate hexahydrate, calcium carbonate monohydrate, vaterite and calcite have been performed during the last nearly twenty years. An overview of these studies is presented.