It is assumed(and often implied) that there are still human parts beneath their suits, meaning they are actually cyborgs, not robots: in "The Tenth Planet", a Cyberman tells a group of humans that "our brains are just like yours", although by the time of "Attack of the Cybermen", their brains seem to have been replaced with electronics. In "Earthshock" (1982), the actors' chins were vaguely visible through a clear perspex area on the helmet to suggest some kind of human face. In "The Tomb of the Cybermen" (1967), veins were visible through the circular head of the Cyberman Controller and in "Attack of the Cybermen" (1985) and "The Age of Steel" (2006), the Cyber-Controller's brain is visible through the dome. The first is a Mondas Cyber Controller, while the second is an alternative cyberman. However, in "Revenge of the Cybermen" (1975), the Doctor says they are "total machine creatures".