Tunable orthorhombic and cubic magnetite nanocrystals (NCs) were synthesized via a simple oxidation-coprecipitation approach with the aid of the interaction of FeSO4·7H2O and C6H12N4 under different reaction conditions.Orthorhombic Fe3O4 nanorods with the average diameter of 15 nm,and lengths of 150 to 200 nm,meanwhile,the as-fabricated cubic magnetite nano -particles have the average grain diameter of 10 nm.