For the first time, nickel nanoparticles are synthesized in reverse micelles by a radiation-chemical method. The particles are shown to be spherical with sizes of an order of magnitude of 1-100 nm. Nickel particles are oxidized by air oxygen to nickel oxide nanoparticles, retaining their shape and nanoscale dimensions. Adsorption of nickel-metal nanoparticles on silica is studied by spectrophotometry.