There have been several seminal storylines, each of which defined the web-slinger during a certain era; these are the ones that are most often adapted into Derivative Works and referenced by later authors.Green Goblin Reborn!: In 1971, the U.S. Department of Health approached Marvel and asked them to do an anti-drug storyline. But there was one little problem: the Comics Code forbade drugs anywhere, both good and bad. Marvel decided to write a three-parter where Harry Osborn was shown to be popping pills and ignore Comics Code approval for those three issues. Along with Green Lantern/Green Arrow doing a heroin storyline the same year, this was one of the first signs of transition to the socially- and politically-conscious Bronze Age of Comics.The Night Gwen Stacy Died: By 1973, Peter Parker's life had settled down a bit. He was in a steady relationship with Gwen, and started getting some respect from the people around him... and then, they dropped the big one.The Green Goblin, who had been revealed to be Harry's father Norman Osborn, kidnapped Gwen. Threatening her in the usual supervillain style, he dropped her off a bridge... and Peter couldn't quite save her. It was recently revealed that Spider-Man's web was the cause of her death, as it caused her neck to break.*Never before had a superhero failed to save their girlfriend from the villain's Death Trap. Unlike many supporting cast deaths, this one had actual consequences. Peter's next door neighbor, kind and feisty Party Girl Mary Jane Watson, who had been one of Gwen's best friends, became more serious and sensitive, and drifted toward a romance with Peter; (though it was later revealed she had always loved Peter from a distance before they even met) the Green Goblin was dead, having accidentally impaled himself as he fought the furious Spider-Man afterwards. For the comics industry as a whole, this was pretty much the sign that the Silver Age was over.The Kid Who Collects Spider-Man: Unlike the other stories here, this isn't a big, world-changing storyline. It's just a single issue (Amazing #248), but it's well-loved as one of Spider-Man's biggest Crowning Moments of Heartwarming. The main story is a fight against a guy named Thunderball, but the memorable part is the backup story where Spidey visits one of his fans and just spends time chatting, even revealing himself as Peter Parker (the kid loves the irony of how Peter sells pictures of himself to Jameson) and explaining how his failure with Uncle Ben drove him to crimefighting. It's only at the end that we learn that the boy is a Littlest Cancer Patient with days left to live, wishing to meet his hero before he passed on.The Alien Costume: In 1984, as part of the Crisis Crossover Secret Wars, Spider-Man got a new, alien costume that responded to his thoughts. Eventually, it was revealed that the costume was a symbiote who was attempting to permanently merge with Peter. He managed to drive it away by exploiting its Achilles Heel, sonic attacks and loud noise in general, whereupon it merged with a reporter who felt Spider-Man had wronged him and became the recurring villain Venom.The Death of Jean DeWolff: In 1986, Spider-Man's friend, police captain Jean DeWolff, was found murdered in her apartment. The hunt for DeWolff's murderer becomes the impetus for an exploration of moral relativism among superheroes, the flaws of the criminal justice system, the desire for vengeance, and the clash of values between the idealistic Daredevil and the pragmatic Spider-Man. This was Peter David's first professional Comic Book writing assignment, and is noted for subverting the comic-book stereotype of Heroic Sacrifice in character deaths.Kravens Last Hunt: The first Spider-Man story to be collected in hardcover (or trade paperback, for that matter), and one of Marvel's first collections. Kraven the Hunter sets out to prove that he's a better man than Spidey, and starts by shooting him and burying him. A multi-title story, and written in a somewhat experimental style.Maximum Carnage: An event from 1993; Carnage recruits C-list villains into a Legion of Doom, and Spidey recruits a number of heroes (and Venom) to stop them. Mainly of note for being the highest-selling multi-title comic series in History (displacing Crisis on Infinite Earths) until Civil War - the reason for such a large mega-run was summarized by writer/E.I.C. Tom DeFalco as being a test to see how a multi-title series would function in the Spidey-verse, something that was tried before, but with a much smaller cast.The Clone Saga: During the '90s, it was felt that Spider-Man had strayed too far from the original concept, gathering a bunch of unrelated cruft onto the premise. So, another Peter Parker showed up, and it was revealed that the Spider-Man we'd been following for the past twenty years was a clone. Through Executive Meddling, the storyline became more and more unwieldy, until the whole thing was undone through a series of retcons and quietly swept under the rug — with the main consequence that the original Green Goblin was back among the living. (Oh, and providing a possibly-dead baby to become Spider-Girl in an alternate timeline.)One More Day: End of JMS Spider-man run. After Aunt May takes a bullet meant for him, Peter becomes so distraught that he's willing to make a Deal with the Devil to fix things. But the price is amazingly steep... Editor Joe Quesada... Er, Mephisto wants to suck all the happiness out of Peter's life, and so demands his marriage to Mary Jane declared null and void. As side effects, Peter's identity (which was public since Civil War) is a secret once more and Harry Osborn is alive again. And of course, writers can start screwing with Peter's love life again.One Moment In Time: A followup story (or OMIT, if you're so inclined), that showed exactly what happened on what was supposed to be Peter and MJ's wedding day, as well as how things fell apart between them after One More Day.Spider Island: An event story from 2011 which spanned all of the ongoing Spider-Man satellite books as well as much of the Marvel Universe. A mysterious viral outbreak grants the whole of Manhattan powers similar to Peter Parkers'. Anarchy soon follows, and things are complicated further as Spidey's old foe The Jackal resurfaces and takes advantage of the chaos with the aid of the enigmatic being known as The Queen. Peter saves the day with help from his fellow superheroes, Mary Jane, and his clone Kaine, and eventually all is right with the world... except in Peters', as his girlfriend Carlie Cooper breaks up with him. The aftermath saw Kaine acquire his own ongoing book series (Scarlet Spider) and set the stage for a future Peter/MJ reunion... sounds all well and good right?Superior Spider Man: A 2012/2013 Spider-Man event that saw the Amazing Spider-Man title dropped and relaunched as the Superior Spider-Man. Following on from the final story arc of ASM, "Superior" sees a new Spider-Man take up the power and the responsibility, only with a vastly superior intellect and a tendency not to pull Peter's normally reserved punches.