A new and a versatile technique have been developed successfully for the preparation of Mg(OH)₂ nanorods without using any additives and/or amines. The technique is based on a simple reaction of magnesium powder and double distilled water at very low temperatures of 100^oC. The formation of nanorods by the reaction of metals with water is suggested to occur due to the decomposition of water. The nanorods so obtained have diameters ranging from 20 to 80nm and their lengths are in micrometers. There are other existing approaches which were applied for the synthesis of magnesium hydroxide nanostructures, but most of the methods involve environmentally malignant chemicals and organic solvents which were toxic and not easily degraded in the environment. Compared with other methods, the present method is simple, soft, inexpensive and environmentally benign which will make it suitable for large-scale production. Therefore, the technique could be extended and expanded to provide a general simple and convenient strategy for the synthesis of nanostructures of other functional materials.