...and we'll take a quick look at a little of it here!
Professor Charles Xavier was a telepath and telekinetic who was one of the most powerful mutant minds on Earth. Charles felt it was his mission to help mutants...
...he did so in X-Men #117 when he faced evil mutant Shadow King (Amahl Farouk) after meeting a young thief (Ororo, later to be known as Storm) in a story by Chris Claremont and John Byrne (reprinted a few times, like in Marvel Masterworks #24 or Classic X-Men #23).
...wherein the pair faced off against Baron Strucker and the agents of HYDRA before Nick Fury joined S.H.I.E.L.D.!
This story was reprinted in X-Men Archives #4, and, yes, the Professor is still in action on his own (pretty much) because he still has use of his legs.
These stories are collected in Marvel Masterworks: The X-Men #7 and in the X-Men Omnibus #1, and this was the inspiration for Charles Francis Xavier to begin to collect the mutants he had been researching together and form a school (as well as a team of agents he could sent into the field to protect people from those who would misuse their power.....).
Much of Professor X's history is combined with the X-Men, not really having a title of his own....though one could say that the X-Men book IS the story of Professor X!
Got My Eye on You
Charles Xavier began to look at young orphan Scott Summers as his first recruit for the X-Men in a back-up series starting in X-Men #38 (November, 1967) to X-Men #43 (April, 1968, all by Roy Thomas and Werner Roth) wherein the Professor and the soon to be Cyclops faced off against the Living Diamond (Jack Winters, who showed up in X-Men #39, December, 1968, which in the main story Scott got his first individual costume) and Scott became the first member of Xavier's team.
All these stories are collected in X-Men Omnibus #2 along with...
These stories are part of the basis for the Sentinels attacking all of mutantkind (though they started their war against mutants back in X-Men #14, November, 1965 by Stan Lee and Jack Kirby), but weren't the end of the Sentinels (nor Cyclops!).
In the early days of the X-Men, Iceman hung around with the rest of the team, occasionally leaving the title to fight the Human Torch, and was trying to get serious with magnetic mutant Lorna Dane...at least until Scott's brother, Alex, showed up.
Iceman and Angel pal around together, co-founding the Champions (along with Ghost Rider, Black Widow and Hercules, which lasted for 17 issues in the mid-1970s written by Tony Isabella, Chris Claremont and Bill Mantlo, and drawn by Don Heck, George Tuska, Bob Hall and John Byrne) in a series that also guested X-Men related people like the Griffin, the Beast, Magneto, Unus, the Blob, the Vanisher, Lorelei and the Sentinels as well as introducing villains Rampage and the Swarm before the team ended (and as a team founded with ex-X-Men and ex-Avengers, and a few loners like Ghost Rider and Darkstar...it at least showed that the West Coast of the Marvel Universe needed protecting!).
Bobby was also the first of the original X-Men to have his own 4 issue mini-series in 1984/1985, and had his origin explored in 2010 in X-Men Origins: Iceman.
Give Me Wings
Warren even went out and tried to be a super-hero on his own, in a back-up series from X-Men #54-56 (March-May, 1969, by Arnold Drake, Roy Thomas and Werner Roth), and almost succeeded in blowing up a city if not for the help of Cyclops and Iceman, which led to Warren joining the X-Men (even though he was the first X-Man to have a small feature outside of X-Men, being an all-new back-up in the last two issues of Ka-Zar's 3 issue reprint title of 1970 and in Marvel Tales #30...stories which were odd as they were written by Superman co-creator Jerry Siegel, and drawn by George Tuska, wherein Angel faced the Dazzler (Burt Worthington, not the discoing Alison Blaire). All these tales are also in the X-Men Omnibus #2!
The plot sounds familiar...
Big And Hairy
Stories also in X-Men Omnibus #2...as well as mostly in Amazing Adventures #17 (a few pages missing in this March, 1973 reprint....with a cover by Jim Starlin, no less).
The Female Is the Deadliest
Jean had a little fact file in X-Men #57 (June, 1969) by Linda Fite and Werner Roth....but, for the most part, Jean's life wasn't really her own....Jean helped Professor X battle the Z'Nox to save Earth....and in that touched a primal force of the universe, the Phoenix (or at least John Byrne teased that in X-Men: The Hidden Years in a bit of retroactive continuity).
This alien lifeforce took the place of Jean when she sacrificed herself to save the team...and became the Phoenix. Sadly, this force went bad and died (in the form of a powerless Jean Grey) devastating Cyclops (who had thought her the love of his life)...