After the events of Schism and Avengers vs. X-Men, the X-Men have broken apart down ideological lines. At the former mansion, Wolverine, poorly suited to the task, headmasters at the Jean Grey School with several other mutants who followed him from Utopia. His goal: teach them to survive in a world that hates and fears them.The Phoenix Five, plus Magneto, led by Scott Summers, are on the run. After using their Phoenix powers to change the world as they saw fit, they're now considered terrorists. Cyclops has them teleporting around the world to rescue or approach new mutants as they manifest. Cyclops' goal: time for a revolution, and he needs an army.Dr. Hank McCoy, dying as a result of further mutations, hears an offhand remark from Iceman, along the order of: "If only Scott could see himself..." and decides that's a brilliant idea. He goes to the past and brings the original five X-Men to the present day in hopes of young, idealistic Cyclops finding a way to get through to current Cyclops. The young X-Men, stunned by the revelation, take a vote and decide to stay to help things become closer to the dream Professor X brought them together to realize. Events progress and it becomes clear that not everything was as they were told upon arriving, in addition to several changes in the team dynamics and emotional impacts, which result in the O5 X-Men and Kitty Pryde deciding to join the New Xavier School in hopes of being able to continue their attempt to bring mutantkind and mankind together.Due to the nature of the series many events cross over and/or happen concurrently with events in Wolverine and the X-Men and with Uncanny X-Men respectively. This book is pretty much essential reading for the Battle Of The AtomBat Family Crossover and the page may contain unmarked spoilers about its conclusion.
In addition to the usual X-Men tropes, this series contains examples of:
Battle Trophy: In a fight with the new Silver Samurai, Beast survives only because Jean and Scott double-team the Samurai. Beast then takes a dropped katana, outright saying that he is so going to keep it.
Cardboard Prison: Mystique breaks out of a super-max prison virtually the day she got in after breaking Lady Mastermind out earlier.
Comic Book Time: Is beginning to become an issue, since it isn't clear what year the original X-Men came from. The stories were originally set in the 60s, but going by the ages of certain characters, it seems they actually came from the 80s instead. Throw Marvel's "sliding timeline" into the mix, and it's anyone's guess when they're from.
Covers Always Lie: Issue 18 has Kitty holding one of the O5 X-Men's suits in a mournful pose, with the rest on the ground around her and feathers falling from above... the issue is actually pretty lighthearted.
Curb-Stomp Battle: The only way to describe over a hundred HYDRA getting beaten by Teen Angel and Modern Angel.
Emergency Transformation: Teen Hank works with Modern Hank to save himself from the mutation that's killing him. In the process, he undergoes another transformation. Still blue and furry, but different.
Five-Man Band: Played with. The O5 X-Men started out as a literal five person team, but the dynamics shifted around once they got to the modern day. They dropped in actual physical numbers once Warren left to join Modern Cyclops' team, but when the entire group defects to his side they're together once again.
Freak Out: Teen Angel after meeting his modern counterpart, at the end of Issue 8.
Teen Cyclops is horrified of the man he has become, and by the world they live in.
Teen Jean Grey is horrified of all that she knows she will go through, but especially the Phoenix-related bits.
Teen Angel is a little wigged out by — if not precisely scared of — his future counterpart.
Subverted with Teen Bobby and Modern Bobby until in Battle of the Atom, they meet versions of themselves from further in the future Ice Wizard and Ice Hulk, and both are a little wigged out. But Teen and Modern Bobby still get along fairly well, and agree on their mutual wigged-out-ness.
Subverted with the Hanks, who are both brilliant and know the importance of working together. Both later gain some issues with their future counterparts Ice Hulk/Ice Master and Future!Beast from the crossover event.
Heroic BSOD: Jean has one when she sees what happens to her future self. Scott has one for a couple issues, after Jean rejects him, Warren has a big one at the end of issue #8. Bobby and Hank have stayed shockingly even-keeled in comparison.
Jean has an even worse one after Angel leaves to join Modern Cyclops.
High Concept: Bendis mentioned early in interviews what the idea of this book was. Literally, "Man what would the kids think about how far this franchise has come?".
Kangaroo Court: When various alien organizations learn Jean Grey is alive again, they seek to prosecute her for her future self's actions as Dark Phoenix.
Knight in Sour Armor: Teen Cyclops has taken on this trait, trying to do as much good as possible despite everyone eying him with suspicion and Jean treating him as if he's done the things his future counterpart did.
Long Lost Brother: Teen Cyclops meeting up with current day Havok, whom young Cyclops thought he'd never see again. A really sweet moment ensues.
Teen Scott and Jean were in love until they got to the future. Now she's not so sure she wants him anymore given what she knows about who/what he grows up to be.
Wolverine is still in love with Jean, even though knowing that this one is way too young.
O5 Hank and Jean kiss. She instigated it on top of that. The events of Battle of the Atom cause a little fallout.
Jeen and Teen Angel have a moment when he catches her when she's falling.
When the helicarrier launched its missile barrage at them, Teen Angel thought it was it for him and started declaring that he had always been in love with Jeen. Fortunately for him, he never had to finish when the rest of the X-Men took down the missiles.
Teen Scott is also mentally thinking over making a move on the Stepford Cuckoos.
Manipulative Bitch: Mystique, starting in issue 7 to Teen Cyclops and setting up a conflict between the O5 and Avengers.
Mind Over Manners: Jean's telepathy shows up unexpectedly due to the stress of seeing the future and knowing her future self dies (more than once). Kitty has to repeatedly remind her it's considered extremely impolite to read minds without permission. Jean apologizes, but her curiosity gets the better of her quite a bit.
Mind Rape: The Stepford Sisters do this to Jean after she tried to do it to Warren again in Issue 11.
Motor Mouth: Teen Bobby tends to chatter, especially when nervous, but also just to hear himself talk it seems.
Mythology Gag: Issue 10 has an illusion of zombified heroes, as a reference to the Marvel Zombies series.
All the Phoenix-touched members of Cyclops' team except Magik at least until later in Uncanny X-Men seem to have intermittent control problems.
Jean Grey's telepathy manifests early as a result of the stress of time travel and finding out about the future, and she frequently has to fight to keep thoughts out of her head.
Swapped Roles: Kitty Pryde, who was 13 and a half when she joined the X-Men, studied under Jean and learned techniques for handling telepathic issues. Now she's an adult, teaching 16 year old Jean from the past those same techniques.
Took a Level in Jerkass: Jeen, who brainwashes Warren into submission twice! And now in Battle of the Atom she manipulates Teen Scott by flattering him (after kissing Hank) to help her stay in the present, which will cause an Apocalyptic Future.
Her actions from a certain point of view arejustified, though, as we are talking about a 15 year old girl whose powers bloomed early along with her Power Incontinence (and her attempts to deal with them and her inexperience in doing so adding to her troubles). The rest of her team survive to the current day, and Jean already knows her future, and that it means her death if she returns to her original time.
What the Hell, Hero?: In issue 8, Jean modifies Teen Angel's behavior after he, understandably, panics and tries to go back home. When Hank tries to call her out on this, she responds with "Henry, don't you of all people start lecturing me on using your God-given things for selfish purposes."
Several character past and present pull this on Modern!Hank for bringing the original 5 forward without much of a plan for what to do with them if they failed to stop Modern!Cyclops in their first encounter. To be fair he was suffering from a mortal illness at the time, but the possibility that he has done more harm than good has come up with some frequency.
Modern Hank gets another one because he didn't give the whole story about the Phoenix possessing Modern Scott at the time when he recruited their younger counterparts.
Jean gets it again after her meltdown when Angel leaves.
The entire O5 team gives one to the Avengers once they find out about the Scarlet Witch and "no more mutants". The Avengers are left on stammering defensive.