A template- and catalyst-free strategy has been successfully designed to prepare MgO and hydrated magnesium carbonate hydroxide (Mg-5(CO3)(4)(OH)(2).4H(2)O) nanosheets with different patterns (such as chrysalides- and rose-like morphology) on the substrate surface. Experimental results reveal that the temperature and substrate allow us to tune the morphology of patterns. Mg-5(CO3)(4)(OH)(2).4H(2)O thermodynamically prefers to grow into the sheet-like crystal at the current solution growth environment, which has been successfully explained by using the chemical bonding theory. The predicted morphology can accord well with the current experimental results. The obtained MgO and its precursor M-95(CO3)(4)(OH)(2). 4H(2)O with novel patterns might find enhanced applications in catalysis, refractory materials, plastics, fire retardants, and functional nanodevices. (C) 2007 Elsevier B.V. All rights reserved.