Vision is not a robot, but a synthezoid, meaning that he is human in every physical way except that he was artificially constructed.

Vision was originally created by the evil robot Ultron to be an adversary of the Avengers, but he quickly turned on his maker and joined the Avengers instead.

After Wonder Man's death, Tony Stark stored his brain patterns on a computer, hoping that one day he could be revived. But Ultron stole the brain patterns and used them as a template to synthesize the Vision.

During his initial encounter with the Avengers, Janet Van Dyne, the smaller-than-normal-human size dynamo known as the Wasp, coins the synthezoid's name. At first sight of the spectral entity, the horrified crusader calls him an "unearthly, inhuman vision."

Vision and the Scarlet Witch marry in Giant-Size Avengers #4 (June 1975). They move to the suburbs, endure the hatred of cul-de-sac bigots who don't want "their kind" as neighbors, and become parents to twin boys, a pregnancy enabled by Wanda's probability-altering hex powers.

The twins are actually missing shards of the soul of the demon Mephisto. The revelation of her children's origin, followed by their loss when they are reabsorbed into him, drives the Scarlet Witch insane.

After the failure of his marriage to the Scarlet Witch, Vision creates a "Synthezoid Family" in the hopes of humanizing himself. He starts with a wife named Virginia and combines their brainwaves to create twin children: Vin and Viv. Later, he even creates a synthezoid dog named Sparky as a pet for the family.

In Avengers: Age of Ultron, Vision is originally conceived as the perfect form for Ultron, but the synthetic body is confiscated by the Avengers and infused with the remnants of Stark's personal AI J.A.R.V.I.S.

Writer Roy Thomas wanted the character to be white as befitting his ghostly name, but printing limitations of the time would have rendered him colorless, with un-inked paper where his skin should be. He settled on red as he did not want Vision to be green like the Hulk or blue like the Atlanteans.

The Modern Age Vision who first appears in Young Avengers #1 (April 2005) is a combination of the old Vision's operating system and the body armor of the time-travelling Iron Lad (who is himself an adolescent time-travelling version of the supervillain Kang The Conqueror).