There are three sub-types of Greys: Type A, Type B and Type C. All Grey aliens appear greyish in color, hence the name "Grey."

Type A:
The most common of the greys. They are also known as _Zeta _Reticuli from the Zeta Reticulan star system. Type A greys have minimal facial features, with large, black eyes being the dominant feature of their over-sized heads. Type A greys typically stand about 4.5 feet tall, with hairless bodies, no discernible ears, and four over-sized fingers per hand. All greys reproduce by cloning. Their social structure is rigid and militant; science and conquering worlds are the prime motivation of the greys. Their prolonged cloning practice has caused them to seek out potential life forms to create an alien/human hybrid.

Type B:
These greys are significantly taller than the Type A (standing about 7-8 feet tall), and come from Orion. Although body proportions and facial features are nearly identical to the Type A greys, Type B greys have a larger, more distinct nose. Considered less dangerous (but still hostile) towards humans than the Type A, the Type B greys have advanced technologies that allow them to perform what would appear to be miracles. Examples of these powers include levitation and the ability to change the molecular structure of objects.

Type C:
The shortest of the greys, Type C greys stand 3.5 feet tall. Very little is known about the Type C, but evidence indicates that the Type C grey share the same ancestry with the Type A _Zeta_ greys. Type C greys are from the Bellatrix star system.