SCIPIO is the passcode to enter Sector Five. When typed in, it summons the Transport Orb to take anyone at the edge of a sector to Sector Five. It can also be used to take anyone in Sector Five's Arena to anywhere in Lyoko's outer sectors.
The password itself is derived from Scipio Africanus, a Roman general who helped bring down the city-state of Carthage in the Punic Wars. Franz Hopper labeled it in one of his books, where Jeremie would later find it and use it to gain access to Sector 5.
The password was first discovered in "Uncharted Territory," after Jeremie's numerous failed attempts to crack it. Surprisingly, the supercomputer didn't use any defensive measures after the numerous attempts of guessing taken.
It would be used fairly often throughout Season 2, due to it being the only way to access the fifth sector. A direct access was later revealed to exist in Franz Hopper, but due to either being utilized or temporarily programmed in by X.A.N.A. Franz Hopper, said direct access remained unusable to the Lyoko Warriors and SCIPIO would continue to be utilized as the access method to Sector Five.
During Season 3, X.A.N.A.'s plot to destroy the Surface Sectors was a major threat. As SCIPIO was the only way the Lyoko Warriors could access Sector Five, if the Surface Sectors were all destroyed, X.A.N.A. would be able to destroy Lyoko's core without interference, rendering the Lyoko Warriors unable to fight X.A.N.A... As such, Jeremie devoted a great deal of research in creating a direct access method of his own in order to circumvent this. After succeeding in doing so at the end of Double Trouble, SCIPIO became obsolete as the conflict with X.A.N.A. shifted focus to investigating the Digital Sea/defending against attempts by X.A.N.A. to lure out Franz Hopper.