Collects X-Men: First Class #11-16 and Giant-Size X-Men: First Class #1. For millions of years, mankind’s place on Earth was unchallenged — until five young people paved the way for a new kind of human! While students at the Xavier School for Gifted Youngsters, Cyclops, Marvel Girl, Angel, Beast and Iceman taught the world what it meant to be X-Men. These are the hidden stories of the team that laid the foundation of a mutant dynasty! In this volume, the fledgling X-Men encounter MACHINE MAN, MEDUSA and the enigmatic MYSTERIO! Guest starring SPIDER-MAN and the FANTASTIC FOUR! Plus, the Beast starts conducting investigations into his own "X" files around the world! Are there aliens among us- or things even weirder?