NOVELTY - Preparing metal oxide nanoparticles involves mixing an anhydrous metal acetate precursor with a non-aqueous organic solvent containing at least one organic stabilizing ligand to form a reaction mixture; heating the mixture to more than 100 degreesC to form metal oxide nanoparticles; and extracting the oxide nanoparticles at a temperature lower than the temperature.    USE - For preparing metal oxide (e.g. zinc oxide, iron oxide, manganese oxide, cobalt oxide, ruthenium oxide, copper oxide, scandium oxide, titanium oxide, vanadium oxide, chromium oxide, molybdenum oxide, yttrium oxide, zirconium oxide, hafnium oxide and nickel oxide) nanoparticles useful in the preparation of formulation e.g. sunscreen, suntan lotion or sunblock to prevent, retard, ameliorate or eliminate photodamage and/or photoaging due to exposure to ultraviolet radiation of the sun; in pharmaceutical formulation, cosmetic formulation, drug formulation, or medicament in combination with carrier, vehicle or excipient; in cosmetic formulation e.g. makeups, topical skin care products, soaps, powders, lotions, creams, ointments, conditioners, shampoos, fragrances, deodorants, deodorizers, hair colors, or hair dyes; in paint formulation; in magnetic recording media, read and write heads, imaging devices, electrical field deposition devices, magnetic devices, optical devices, or thin films; in rubber, plastics, polymers, ceramics, adhesives, mastics, sealants, lubricants, metal protective coatings, cigarette filters, foods, food packaging materials, ferromagnetic materials, batteries, fuel cells, photocells, thermoelements, components in silicate compositions, fungicides, cement, paint, plastics, lubricant, fungicide, silicate composition, magnetic device, optical device, electrical field deposition device, imaging device, thin film (all claimed).    ADVANTAGE - The monodisperse and stable particles have uniform size (preferably 3 - 20) nm. The manganese oxide nanoparticles have size of 3 - 20 (preferably 12 - 20) nm.    DETAILED DESCRIPTION - Preparing metal oxide nanoparticles involves    (a) mixing an anhydrous metal acetate precursor with a non-aqueous organic solvent containing at least one organic stabilizing ligand to form a reaction mixture;    (b) heating the mixture to more than 100 degreesC to form metal oxide nanoparticles decomposing the acetate; and    (c) extracting the oxide nanoparticles into a hydrocarbon solvent by precipitation with a flocculating agent at a temperature lower than the temperature of step (b).    INDEPENDENT CLAIMS are also included for    (1) use of Mn3O4 nanoparticles for production of superlattices or magnetoresistive oxide thin films; and    (2) use of zinc oxide nanoparticles for preparation of laser material and thin film.