Typically, possession in science fiction involves extraterrestrial parasitic organisms that can take control of a human host.
[1][2] In Robert Heinlein's novel The Puppet Masters, slugs from Titan, the largest of Saturn's moons, can take over human bodies[1][2] and know everything their hosts know.
[citation needed] In Invaders from Mars, mind-control crystals at the base of the skull enable the Martians to turn their victims into saboteurs.
[citation needed] In the Star Trek universe, the Trill are a symbiotic pair of species consisting of symbionts and hosts.
The symbiotic species can also control human beings, but not for extended periods of time (see episode "The Host" of Star Trek: The Next Generation).