The legendary X-Men were founded by Professor Charles Xavier, a mutant telepath who had spent many of his adult years studying mutation. Following an encounter, Xavier became determined to protect the world from the threat of evil mutants as well as foster a world that would enshrine peaceful coexistence between humans and mutants. He eventually decided to start a school for mutants and train them to be what would eventually become the X-Men.
Charles turned his father's estate into Professor Xavier's School for Gifted Youngsters. His earliest student was Jean Grey , who was only twelve years old when her mental powers manifested. He constructed the Danger Room to test mutants, and developed Cyberno, a prototype mutant detector that was later replaced by a more powerful machine called Cerebro.
After years of preparation, Charles decided that it was time to recruit the young mutants of whom he had been keeping track when anti-mutant hysteria had hit its peak. Charles traveled to Washington D.C. and sought out an FBI agent who was assigned to investigate reports of mutants. Xavier convinced him to allow him to attempt to enroll young mutants in his private school and train them to battle evil mutants.
In the following days, Charles recruited Scott Summers, rescuing the boy from the clutches of an evil mutant. Scott became the first of the X-Men, operating under the code name Cyclops. Later, Charles also had Jean Grey join as Marvel Girl.
The original Team of X-Men had Cyclops, Phoenix, Beast, Iceman and Angel. Soon thereafter a lot of classic X-Men were discovered, such as Storm, Wolverine, Nightcrawler, Colossus and Kitty Pryde. Later, Magik joined the team as a new mutant, and Rogue came from the Brotherhood of Mutants and Gambit from Sinister's Marauders. Another ex-villainess becoming an X-Men member was Emma Frost. And so many others have indentified themselves with the X-Men cause and decided to join as well, like Psylocke and Cable.