Novel properties may arise when lowering the dimensionality of materials because of the quantum confinement effect and the reducing of neighbor atoms. In this talk I will present different approaches to grow nanomaterials (metal, metal oxides, chalcogens and metal chalcogenides) inside boron nitride and carbon nanotubes (NTs). The spatial confinement of NT’s cavity promotes and stabilizes the formation of nanostructures with new phases and geometries. The encapsulation of nanotube walls protects the core materials from the chemical oxidation with the environment, which has been shown to have detrimental effects on the structure integrity and physical properties of the nanomaterials. The encapsulated materials are very mobile and they rotate, twist and shuttle inside nanotube channels. The nanomaterials filled nanotube system resembles the nanoscaled test-tube, which enables various in-situ studies of nanomaterials growth and interactions.<div id="UMS_TOOLTIP" style="position: absolute; cursor: pointer; z-index: 2147483647; background-color: transparent; top: -100000px; left: -100000px; background-position: initial initial; background-repeat: initial initial;"> </div>