Water-in-oil, w/o, microemulsions, human and environmentally friendly, were used to synthesize zinc oxide, ZnO, nanopowders based on a simple process. The synthesis route consisted in using w/o microemulsions, where the continuous phase was emu oil, whereas the discontinuous phase was a 0.5 M zinc acetate aqueous solution, both stabilized by a layer of surfactant molecules of a 1:1 Span 80 and Tween 80 mixture. The precipitation is reached with the addition of a 1.0 M aqueous solution of sodium hydroxide. The resultant precipitates were dried at 100 degrees C in air and then calcined at 800 degrees C during 2 h. The procedure allowed the obtaining of nanoparticles with an average size of around 31.2 nm, with reduced polydispersity and pseudo-spherical morphology. The zinc oxide powders were characterized by X-ray diffraction, scanning and transmission electron microscopy, confirming the hexagonal wurtzite phase of ZnO. (C) 2017 Elsevier B.V. All rights reserved.