Noticing of the extremely low volatility of ionic liquids, the authors attempted to make metal vapor deposition to the liquids and observation of it with an electron microscope. We discover that the ionic liquids can be observed by electron microscopy because there is no problem of charging and that the metal vapor deposition to the liquids generates stable metal nanoparticles in the liquid. The former discovery allows us to observe insulating materials by electron microscopy by wetting the samples with ionic liquid. The size of metal nanoparticles obtained by vapor deposition was found to depend on the kinds of ionic liquids. These findings suggest various applications in nanotechnology field.