Visual observation of gas hydrates at the microscopic scale in synthetic porous media provides unequivocal visual evidence that clathrates can form in systems without the presence of a free-gas phase. Hydrates were formed from a soluble liquid hydrate former (tetrahydrofuran, C4H8O), from free gas (CH4), and from dissolved gas (CO2). Clathrates were found to form within the center of pore spaces, rather than on grain surfaces. Cementation of grains only occurred in regions of a small grain size, or where a large proportion of pore space was filled with hydrate. However, even at high clathrate saturations, a thin film of free water persisted on grain surfaces. The results have important implications for the potential cementing effect of hydrates on sediments, and thus for sediment permeability, slope stability, and seismic interpretation of hydrate-bearing sediments.