query: When were the X-Men first introduced by Marvel?
passage: X-Men
Within the Marvel Universe, the X-Men are widely regarded to have been named after Professor Xavier himself. The original explanation for the name, as provided by Xavier in The X-Men #1 (1963), is that mutants "possess an extra power ... one which ordinary humans do not!! That is why I call my students ... X-Men, for EX-tra power!"[4]
passage: X-Men
There were many new popular additions to the X-Men in the 1990s, including Gambit, Cable, and Bishop. Gambit became one of the most popular X-Men, rivaling even Wolverine in size of fanbase after his debut in Uncanny X-Men #266 (Aug. 1990). Many of the later additions to the team came and went, such as Joseph, Maggott, Marrow, Cecilia Reyes, and a new Thunderbird. Xavier's New Mutants grew up and became X-Force, and the next generation of students began with Generation X, featuring Jubilee and other teenage mutants led and schooled by Banshee and ex-villainess Emma Frost at her Massachusetts Academy. In 1998, Excalibur and X-Factor ended and the latter was replaced with Mutant X, starring Havok stranded in a parallel universe. Marvel launched a number of solo series, including Deadpool, Cable, Bishop, X-Man, and Gambit, but few of the series would survive the decade.