A low-energy new method based in a one-step synthesis at room temperature produces very small maghemite nanoparticles. The fast neutralization reaction (co-precipitation) of a ferric solution (FeCl 3 aqueous) in a basic medium (NH 4 OH concentrated) produces an intermediate phase, presumably two-line ferrihydrite, that in oxidizing conditions is transformed to maghemite nanoparticles. That "primordial soup" is characterized by small atoms arrangements, that are the base for maghemite tiny crystals. The final product of the reaction was characterized by X-Ray Diffraction, High-Resolution Transmission Electron Microscopy, X-ray Absorption Fine Structure, Mössbauer spectroscopy, and magnetometry.