Thomas "Tommy" Shepherd was born and raised in Springfield, New Jersey. He is only son of Frank and Mary Shepherd, who divorced when he was still young. Tommy was in and out of juvenile halls for most of his life. It was in one of the detention centers that Tommy first met Lisa. The two seemed to have had some kind of romantic or physical relationship during this time.
Because Tommy "accidentally" vaporized his high school using his powers, he was imprisoned under court order in a high-powered facility equipped with advanced offensive and defensive technology such as robotic suits and power dampening containment cells. Before the Young Avengers freed him, Tommy had been locked up for months, and was being tested and experimented on with the goal to make him into a living weapon.
The team was able to locate him in a high security detention facility for superpowered juvenile offenders. They release him from his cell, and Stature almost immediately noted that Tommy and Billy could be twins. The breakout did not go unnoticed, and as the team ran into the armed officers of the facility. Tommy cynically and cruelly began attacking the officers and fleeing doctors, but was stopped by Kate Bishop and Patriot.
Speed helped the team in battling both Kree and Skrulls soldiers to rescue Hulking. After the battle, Tommy officially joined the team and adopted the codename "Speed". Speed was anxious to be a hero, and was the first to alert the Young Avengers that the villainous team, the Zodiac, was attacking the United Nations.
When the Runaways tried to stay out of the conflict, they barely managed to escape from the government forces. Hearing of this development in the news, the Young Avengers decided to help the Runaways even though Captain America vetoed the plan. Wiccan used his magic to locate and teleport to the Runaways. However, the Runaways believed that the Young Avengers had come to capture them and a fight ensued until Patriot succeeded in convincing Nico Minoru to stop the hostilities. Speed develop a close sibling-like friendship with Molly Hayes.The two teams were later attacked by Marvel Boy, who captured Wiccan, Karolina, and Hulkling, and almost killed Xavin. The young heroes became the prisoners of the Warden, who proceeded to practice vivisection on the unconscious Teddy. The boys were rescued by Xavin, whose Skrull physiology allowed him to recover from Noh-Varr's attack. Billy came close to killing the Warden, but Teddy stopped him.
When the Skrulls invaded Earth, Speed joined the other Young Avengers and Runaways on the front lines of the battle. Speed and Wiccan saved Hulkling from execution and later assisted Xavin to again rescue Hulkling.
During the Siege of Asgard, Tommy was the armor-bearer for Tony Stark. Speed along with the other Young Avengers helped rescue the fallen from warriors and civilians after the battle. Speed was pushing himself hard but still felt like he was failing until Ronin found him. He simply let Speed know that giving it his all would always be enough.
After Wiccan's powers overloaded and the Avengers decided to keep him under observation, Speed and the other Young Avnegers broke Wiccan out of holding and began the search for the Scarlet Witch. Accompanied by Magneto the team travelled to Transia where they met Quicksilver and a fake Wanda, who was revealed to be a Doombot. Wiccan teleported himself into Latveria and discovered a depowered and amnesiac Wanda engaged to Doctor Doom. The Young Avengers, Magneto and Quicksilver went after Wiccan, as well as the Avengers. A battle with Doom's Doombot army soon broke out and was only stopped by the arrival of Iron Lad.
Iron Lad teleported the Young Avengers and Wanda into the timestream. They all went into the past, and met a reanimated Jack of Hearts, who exploded. After that, Wanda remembered who she was, regained her powers and returned herself, the Young Avengers and Scott Lang into the present. She then finally confirmed that Billy and Tommy were indeed her reincarnated sons.
Sometime after their induction into the Avengers, the Young Avengers again decided to disband largely at Wiccan's urging. Teddy and Tommy moved in with the Kaplans, but Tommy moved out a short time later. As the other Young Avengers stayed away from heroic activities, he separated from them. He was hired by a company hiring superpowered beings, assembling electronic components at a superhuman speed (five minutes equalling to a month of work) for a few weeks and saving that money to travel for a few months, before repeating the cycle.
In that company, he met David Alleyne, the depowered mutant formerly known as Prodigy and started hang out with him. Soon after, someone broke into the company building, under the guise of Patriot. After having confirmed that Elijah Bradley wasn't involved, Speed decided to inquire about it, and took Prodigy with him. Waiting for him at night, the duo confronted the entity, and Speed was seemingly dematerialized by the attacker.
Speed is a mutant with an enhanced physiology design for supersonic speed, including:
Superhuman Speed: Speed can run, move and react at speeds far greater than the average human. His top running speed is unrecorded, but it is demonstrated that he can at least achieve supersonic speeds. It is unclear if his running ability exceeds that of Quicksilver given that the adult speedster was carrying Wiccan over his shoulder and was on a conversation with him during the friendly challenge issued by Speed.
Molecular Acceleration: He can also generate hyper-kinetic vibrations that accelerate the molecules in matter, causing any solid object he directs his vibrations at to explode.
Intangibility: He also can use molecular destabilization to walk through solid objects.
Superhuman Stamina: Speed's physiology grants him greater stamina when compared to an ordinary human, allowing him to operate at peak capacity for at least several hours before he begins to grow tired.
Superhuman Agility: Speed's physiology grants him superhuman agility being more flexible and having greater balance.
Superhuman Reflexes: He's capable of reacting fast, because he's moving at superhuman speeds everything moves slower for him.
Superhuman Durability: Speed's physiology also provides him with limited protection against impact forces and the high levels of friction that are produced when he moves at superhuman speed.
Superhuman Strength: Speed possesses a limited degree of superhuman strength, allowing him to lift about 800 lbs with his arms and 1 ton with his legs.
Wiccan first reached this conclusion after meeting Tommy, his identical twin except for the white hair. After reviewing intelligence files from the Skrulls and Avengers about Thomas and William, Billy decided he and Tommy must be Wanda's children reincarnated. He based this on their names, appearances, Tommy's white hair and speed matching his "uncle" Pietro, and Billy's powers being similar to Wanda's.
The Scarlet Witch finally confirmed that Billy and Tommy were indeed her reincarnated sons.
Although initial skeptical about the relationship, Speed later embraced and enjoyed the new twin relationship with Wiccan.
Speed and Kate Bishop have share mutual attraction to one another, creating a love-triangle between themselves and Patriot.