We describe a new technique using microemulsions to produce ultrafine precursors of yttrium iron garnet. A coprecipitation of hydroxide or carbonate precursors was made in a W/O microemulsion medium. These precursors (ca. 3 nm in size), when heated above 700 degrees C, transformed to YIG phase. Once prepared, YIG nanoparticles were characterized by X-ray diffraction, transmission electron microscopy and de magnetic measurements.