Devirtualization is the process of being materialized back to the real world from Lyoko. Once a warrior is virtualized, there are mainly three ways to get back out:
Defeat: The warrior loses all of their life points and the warrior's virtual body is discarded. The Lyoko Warriors can lose life points by either being hit by being attacked by a friend or foe, to be smashed by a large object or by falling from great heights. The person seems to vanish, leaving the framewire of their body behind, as well as some light blue squares. The person then exits Lyoko through the Scanner again. After that the user can't be re-materialized for another 12 hours.
Return to the past: Returning to a past point in time, the warriors end up in a location or a point of time where they weren't virtualized.
Devirtualization program: A program to move the warrior back from Lyoko to the real world. The operator (usually Jeremie or Aelita) is able to execute a series of commands to bring a given character back to the real world. Essentially, this program is the reverse of the Virtualization program.
CODE: EARTH: In Season 1 and 2, Aelita was required to enter a Tower while Jeremie launched a special program for her to be properly devirtualized. This was later no longer needed when Aelita gained her memories and became complete.
Once or twice it happens that a character has to be devirtualized in an emergency. When one goes over the edge and threatens to land into the digital sea, if Jeremie is fast enough he can get them out before they enter the Digital Sea. This is done once or twice, with at least once in which Jeremie mentiones to the rest to remind him to "boost the power on that program". It also seems that getting devirtualized can be pretty painful.
In the episode Spectromania, Jeremie explains that after being devirtualized by an enemy, they cannot be virtualized again for twelve hours.
Ninjas: The same as the Lyoko Warriors, but the pixels turn green.
Monsters (except for Guardians and Kolossus): Seasons 1-4: The monster explodes into colored geometric objects, and the objects flicker away. For monsters who can't fly, they blow into pieces and the remnants of their bodies disappear.