adopting the strategy of dissolution-recrystallization under hydrothermal conditions (at 240 degrees C for 72 h) in the presence of a triblock copolymer (Pluronic P123), we fabricated nano- and microparticles of single-crystalline MgO of rectangular parallelepiped and hexagonal prism morphologies. The MgO crystallites display three-dimensional wormholelike mesopores and have a surface area as high as 298 m(2)/g even after calcination at 550 degrees C for 3 h.