Scott Summers was the first of two sons born to Major Christopher Summers, a test pilot for the U.S. Air Force, and his wife Katherine. Christopher was flying his family home from vacation when their plane was attacked by a spacecraft from the interstellar Shi'ar Empire. To save their lives, Katherine pushed Scott and his brother Alex out of the plane with the only available parachute. Scott suffered a head injury upon landing, thus forever preventing him from controlling his mutant power by himself.
With their parents presumed dead, the authorities separated the two boys. Alex was adopted, but Scott remained comatose in a hospital for a year. On recovering, he was placed in an orphanage in Omaha, Nebraska that was secretly controlled by his future enemy, the evil geneticist Mister Sinister.
As a teenager, Scott came into the foster care of Jack Winters, a mutant criminal known as the Jack O'Diamonds. After Scott began to suffer from severe headaches he was sent to a specialist who discovered that lenses made of ruby quartz corrected the problem. Soon after, Scott's mutant power first erupted from his eyes as an uncontrollable blast of optic force. The blast demolished a crane, causing it to drop its payload toward a terrified crowd. Scott saved lives by obliterating the object with another blast, but the bystanders believed that he had tried to kill them and rallied into an angry mob. Scott fled, escaping on a freight train.
Winters sought to use Scott's newfound talent in his crimes, and physically abused the young boy when he initially refused. However, Scott's display of power had attracted the attention of the mutant telepath Professor Charles Xavier, who teamed up with F.B.I. agent Fred Duncan in their mutual attempt to find Scott. Scott was rescued from Winters' clutches and was enlisted by Xavier as the first member of the X-Men, a team of young mutants who trained to use their powers in the fight for human/mutant equality.
As Cyclops, Scott became deputy leader of the X-Men. While he was a skilled tactician, his social skills were lacking. Scott had fallen in love with his teammate Jean Grey, but his reserved demeanor prevented him from expressing his feelings for her for years. When Xavier's other original recruits left the fold following an encounter with the sentient island-being Krakoa, Cyclops stayed on as deputy leader of the new team.
Shortly thereafter, the cosmic entity known as the Phoenix Force took Jean's place. When it committed suicide, Scott believed the love of his life had died and he left the X-Men. During his time away from the team, Scott met fishing boat captain Lee Forrester who helped him work through his grief. Scott eventually returned to the X-Men whereupon he met Madelyne Pryor, a woman who bore an uncanny resemblance to Jean. Unaware that Madelyne was a clone of Jean created by Sinister, Scott fell in love with Madelyne and they were soon married. Madelyne fell pregnant and bore Scott a son named Nathan Christopher.
When the real Jean emerged from suspended animation, Scott abandoned his wife and son and rejoined the other original X-Men in establishing a new team, X-Factor. During a demonic invasion of New York City, X-Factor and the X-Men fought against a super-powered and insane Madelyne. The invasion was thwarted after Madelyne perished in combat with Jean.
Later, the mutant warlord named Apocalypse infected baby Nathan with a techno-organic virus. To save his son's life, Scott had to allow a member of the Clan Askani to transport Nathan two millennia into the future, where it had been foreseen that he would deliver the world from Apocalypse’s clutches. X-Factor disbanded soon after, and its members returned to the ranks of the X-Men. Scott and his long-time love Jean were married, and whilst on their honeymoon their spirits were taken into the timestream by the Clan Askani’s matriarch. Arriving in the future, they inhabited new bodies and raised Nathan for twelve years. When they returned to their own time and bodies, Nathan remained in the future and ultimately matured into his time's greatest hero: Cable.
Following Professor X's arrest for crimes committed as the evil psionic entity Onslaught, Scott assumed the role of leadership of the X-Men once more. Soon after, the government sponsored mutant-hunting operation known as "Zero Tolerance" took effect, and the villainous Bastion captured the X-Men. In his attempt to destroy mutantkind, Bastion placed a nanotech bomb inside Scott's body. The X-Men escaped, and the mutant doctor named Cecilia Reyes saved Scott's life. Scott and his wife soon took a leave of absence from the X-Men for a period of recuperation.
Not long after returning to the team, Scott and Jean soon found themselves embroiled in Apocalypse's bid for cosmic power by assembling "The Twelve" - a group of mutants who would determine the fate of their kind that included Scott, Jean, and Cable. They were wired to a machine that would channel their awesome energies into Apocalypse, allowing him to absorb the body of the time-tossed powerful mutant teenager known as X-Man. As his teammates fell around him, a powerless Scott saved X-Man and merged with the would-be conqueror to create a new evil entity. Jean detected Scott's psyche inside Apocalypse and prevented the X-Men from destroying him, however he was presumed dead by most of his teammates. Only Jean and Cable refused to believe Scott had perished.
Investigating rumors he was alive, the pair found him in the birthplace of Apocalypse in Akkaba, Egypt, struggling to reassert his mind over the villain's psyche. Ultimately, Jean was able to physically rip Apocalypse's essence from Scott's body using her mental powers, and Cable destroyed it with his own powers.
Scott left for a small period of recuperation, during which he met and reconciled with his father. Afterwards, Scott returned to the X-Men, but his association with Apocalypse had given him a grimmer, more serious personality than ever before. As a result, many of his relationships became strained, including his marriage to Jean. Scott sought the counsel of his teammate Emma Frost and the pair began a psychic affair. When Jean discovered Scott's betrayal, he left the X-Men in order to sort out the mess his life had become.
Following the outing of Professor X as a mutant to the world, his school was rechristened the Xavier Institute of Higher Learning and opened its doors to the mutant population at large, training and educating dozens of young new students to help them cope with their burgeoning abilities. After the death of his wife, Scott assumed the position of co-headmaster of the School alongside his new love, Emma.
Cyclops's world was further upset when a mysterious mutant attacked and brought him and Marvel Girl (his and Jean Grey's daughter) to a secret abandoned facility. Cyclops eventually discovered that the mutant was none other than his brother Gabriel, who had been a student of Moira's that Professor X had sent to rescue Scott from Krakoa. Scott had witnessed the apparent deaths of Gabriel and his teammates; Xavier had mind-wiped him to alleviate the psychic trauma of the event. Shaken to the core, Cyclops expelled the then powerless Xavier from the Institute.