The Greys do not have organs as humans do, but rather a network of microscopic cell-clusters that communicate with electrical impulses across their entire 'body' - a relatively shapeless jelly that exists purely in water. The basis of advanced evolution in the Greys, and further to their technologies, is the 'fortification' of the electrical/mollecular bonds, creating solid forms and complex constructions from telepathic commands. Their forms are limited to their mental control, and their immediate access to water. They are able to survive on any planet that can sustain water by adding water to their mass. For example, on earth, Grey must surround himself in a 'suit' of water that gradually evaporates in the sun and must be replenished. With his advanced skills, he may use any body of water to enhance his form and 'fortify' it into objects. These abilities are limited to only a few highly skilled operatives, most of the species naturally have only the ability to sustain their own form, and perhaps simple constructions, so must use technology for everything else.