Chris Claremont, Louise Simonson, and Gerry Conway (Writers); Jim Lee, Walt Simonson, and Tom Sutton (Artists)
Collects three "mutation" stories. See how Beast gained his fur -- how Angel became Archangel -- and how Psylocke became the Asian ninja we all know today.
Amazing Adventures (Vol. 2) #11 and #17, X-Factor (Vol. 1) #15 and #24-25, Uncanny X-Men #256-258