By early 1963 the foundations of the Marvel Universe had been laid. Following the introduction of the Fantastic Four in 1961 came the amazing (Spider-Man), the astonishing (Ant-Man), the strange (Doctor, that is), the incredible (Hulk), the invincible (Iron Man) and the mighty (Thor). Still, Marvel editor in chief Stan Lee realized something was missing. “I was writing these characters and I thought it would fun to put them together in a team,” he recalled. So Lee and artist Jack Kirby assembled Iron Man, Ant-Man and the Wasp, Thor, and the Hulk to create the Avengers. Right away it was clear this team was different. If the Fantastic Four were family, then the Avengers were the co-workers you didn’t choose. Not everyone got along—the Hulk fought with everyone—but working together they could defeat the baddest of Marvel’s bad guys, like Loki, Kang the Conqueror, the Masters of Evil, and Immortus. The lineup was ever changing: The Hulk departed, Captain America joined, and Ant-Man grew up to become Giant-Man. Then, remarkably, villains Hawkeye, Quicksilver, and the Scarlet Witch became heroes—and Avengers—and the group’s founding members shockingly departed, leaving Captain America to lead the newly-minted heroes.