The decomposition of metal (Ti, Zr, Sn) alkoxides at 250°C in a solution of tetradecene and dodecylamine resulted in the formation of ultra-small (1–2nm) oxide nanoparticles. The nanoparticles showed unusual structural properties. The high-pressure orthorhombic phase was found for SnO 2 . The as-synthesized ZrO 2 nanoparticles were only partially crystallized. It was possible to observe their in situ crystallization under the TEM beam. The TiO 2 nanoparticles appeared amorphous, with only a few nanocrystals dispersed in the sample. The temperature evolution of the samples was investigated in situ by Raman spectroscopy. All SnO 2 was converted to stable cassiterite at 350°C. TiO 2 and ZrO 2 samples displayed phase stability reversal over a broad range of temperatures.