Phase transformation of boehmite (AlOOH) nanostrips to alpha-Al2O3 nanolaces was investigated under electron beam irradiation of a 200 keV transmission electron microscope (TEM). X-ray diffraction pattern showed that the powder consisted of boehmite phase before the electron exposure, while selected area electron diffraction patterns demonstrated the formation of stable alpha-alumina phase after bombardment with high-energy electrons. The in situ TEM observations revealed that the initial morphology remained unchanged while a lace-like mesostructure of alpha-alumina was developed.