Gas hydrates can be free floating in the sediment matrix; contacting, but do not cement; actually cementing and stiffening the sediment. The microstructure and growth of gas hydrates (CH4 and CO2) in porous media were observed in situ by Magnetic resonance imaging (MRI). The experimental results confirmed the random nucleation of gas hydrates in porous media. The results show that hydrates are preferentially formed in the pore spaces. Hydrates then occupy the pores of porous media gradually, but do not cement the adjacent glass beads in the final stage. Gas hydrates are believed growing as free-floating model in porous media. (C) 2014 Elsevier B.V. All rights reserved.