- It's one of the first things they teach you in medical school. It means , 'First, do no harm'.
- — Pieter Cross src
In Sogndal, Norway, the pregnant wife of noted surgeon Theodoric Cross was attacked by vagrants, but saved by Dr. Mid-Nite. She went into labor, and Mid-Nite delivered the baby boy, whom she named Pieter. Pieter grew up to be a brilliant doctor, graduating Harvard at age 19, and later immigrating to America and working under Dr. Charles McNider (Dr. Mid-Nite). Pieter began investigating A39, an accidental derivative of the steroid-like Venom, which was plaguing the residents of Portsmouth City.
Pieter found that the powerful narcotic was being produced by an evil corporation called Praeda Industries, which in turn was ran by the Terrible Trio. The drug lords behind A39 knocked Pieter out, injected him with the drug, and placed him behind the wheel of a moving car. Pieter woke just as the car struck and killed a woman. The drug had left him blind, but gave him the ability to see in the dark instead. He then took on the identity of his long time mentor Dr. Mid-Nite, and brought the drug lords to justice, eventually joining the JSA.
Aboard Hourman's timeship, Metron explained to Mid-Nite and the JSA that Extant used Metron's stolen Mobius Chair to travel to the end of creation and create a new universe of his own making. Unless the JSA stopped him, Extant's new universe would go backwards through time and erase the current universe.
Dr. Mid-Nite and Black Canary went on a date at Coney Island and discussed where their relationship was going.
During the Imperiex War, Mid-Nite, the JSA, and the JSA reserves were given a mission by President Luthor to disrupt Imperiex's link to his ship's power supply. The JSA not only cut off Imperiex from his power, but they managed to blow up his ship as well.
Mid-Nite and Mr. Terrific examined a woman under a sleeping spell that their JSA teammate Dr. Fate believed to be his wife Lyta. They had no idea how to treat her, so Fate lost his temper and stormed off to search for his own solution.
Mid-Nite got caught up in a battle between Atom-Smasher and probationary JSA member Black Adam. Captain Marvel arrived at JSA hq and physically restrained Black Adam, calming him down in the process. Because of a dispute between the current JSA chairman Sand and Hawkman, the JSA elected Mr. Terrific as their new JSA chairman, and immediately afterwards Mid-Nite and most of the JSA were teleported by Roulette to her House.
Roulette forced Mid-Nite and his JSA teammates to battle each other for the amusement of a crowd of super villains. Mid-Nite and Mr. Terrific were strapped into chairs and pitted against each other in a game of chess, with Roulette promising death to the loser. Mid-Nite and Terrific intentionally played to a draw, then escaped. The JSA wrecked Roulette's House, so she teleported them back to JSA hq with a promise that they would play in her games again.
Mid-Nite and the JSA next investigated the death of super villain Shakedown. Batman joined them, letting them know Shakedown and his partner New Wave had kidnapped Jessica Weintraub, the infant daughter of a recently bankrupt Gotham computer whiz. When the villains realized they weren't going to get paid their ransom they turned on each other. Batman and the JSA saved Jessica and captured New Wave. Black Canary left the JSA and told Mid-Nite she needed to break off their relationship because an old flame had reentered her life.
Mid-Nite gave new JSAer Power Girl a full physical and determined that her powers were not magic-based as she previously believed. Mid-Nite and the JSA welcomed Johnny Thunder, who claimed to have had a miraculous recovery from Alzheimer's. In truth it was the Ultra-Humanite in possession of Thunder's body.
The Ultra-Humanite used Johnny Thunder's Thunderbolt to conquer the world, and imprisoned Mid-Nite and virtually every superhuman on Earth in stasis tubes, only reviving them when he needed mind-controlled slaves to serve in his personal guard: The Thunderfront. Mid-Nite served as a member of the Thunderfront when they attacked the JSA, the only heroes not under the Humanite's control. The JSA used a device that disrupted the braincaps Humanite used to control the Thunderfront, freeing them from Humanite's mental domination. Mid-Nite and the JSA later defeated the Humanite, and afterwards attended the funeral of Johnny Thunder, whose body gave out after he was freed from the Humanite's control.
Dr. Mid-Nite is one of the most prominent physicians in the world, along with his JSA teammate and colleague Mister Terrific. They are often called upon when an autopsy is needed, or when a hero needs major surgery. In this roll Pieter has accomplished many notable achievements including: determining that Alan Scott was composed of the green flame of the Starheart; giving Power Girl her annual checkups, as well as testing her powers; emergency surgery on Hourman; removal of the Brainiac virus from Oracle; the autopsy of Sue Dibny and removing the sniper bullet that wounded Lois Lane in Umec. He is also called upon by other medical agencies, such as S.T.A.R. Labs, when medical emergencies or dilemmas appear. 
Mid-Nite went to the Gotham General Hospital along with Mr. Terrific to take care of Selina Kyle after Hush removed her heart from her body. When Batman recovered the heart, Mid-Nite and Terrific performed a successful surgery on Selina to put her heart back, but afterwards, they weren't sure if she would ever be Catwoman again.
Since his sight was restored, Pieter could not effectively use his blackout bombs, as he couldn't see any more than his targets could. Furthermore he felt more blind than ever as he had less ability to see than he did prior to his returned sight, and thus could not perform surgery on Lance when he was mortally wounded, or determine the accuracy of a patients ailment when he returned to work at the hospital.
When the rebellious half of the JSA shows up to tell the other half what Gog is doing to the planet, a battle ensues. For the JSA's defying of Gog and his will, he undoes all the "miracles" he has done for them. Thus returning Cross's blindness.
As a result of a serum injection, Cross's eyes, visual processing, and dexterity were permanently altered and enhanced, without any negative side-effect.
- Enhanced Vision: He can see and sense everything that is around him, allowing him to keep flawless tab of his surroundings without trouble. His vision is incomparable. Everything is much sharper, and more defined. His vision is unhindered by darkness or brightness, thus he is always able to see clearly and comfortably without harm. He has much better depth perception than normal humans and can even and react to movements that are too fast for normal humans to notice. He can percieve all movements with perfect clarity without strain, colors are also much more vibrant. Normal healthy human vision is considered blind or mud-eyed in comparison. His sense of sight exceeds by far that of a hawk and eagle: He can see objects in microscopic detail, and can see into the invisible spectrum of light. His enhanced vision allows him to see and process the smallest details easily, and extends into the infrared region of the light spectrum.
- Enhanced Dexterity: The serum increased the speed and precision of the his hand-eye coordination dramatically. Allowing him to be able to perform his surgeries quickly and flawlessly. He became able to, by hand, rapidly draw high-resolution images with flawless details, almost as if photographed, without ill effect.
- Genius Level Intellect: Cross is also highly intelligent, thought to be the second most intelligent person on the JSA (after Mister Terrific) by Rulette. She chose him to face Mister Terrific on a deadly chess game.
- Animal Training: Doctor Mid-Nite owns a pet wood owl, which he named Charlie. Charlie was named after Cross' mentor and predecessor, Charles McNider.
- Martial Arts
- Medicine: Doctor Mid-Nite is the world's most prominent superhero doctor. As a top physician Cross is capable of all maner of various surgeries, including doing it in the dark. He is often called upon when an autopsy is needed, or when a hero needs major surgery. Among Cross' notable achievements as a physician includes determining Alan Scott was composed of the green flame of the Starheart, giving Power Girl her annual checkups as well as testing her powers, emergency surgery on Hourman, removal of the Brainiac virus from Oracle, the autopsy of Sue Dibny, and removing the sniper bullet that wounded Lois Lane in Umec. He is also called upon by other medical agencies, such as S.T.A.R. Labs, when emergencies or dilemmas appear.
- Specialized Lenses: Utilizing special infrared lenses, also equip special ultrasonic lenses, as well as receive images from a camera strapped to his owl, Charlie.
- Gauntlets: Cross's gauntlets carry a wide variety of chemicals, medicines, and small-scale equipment.
- Blackout Bomb: A small bomb which release pitch-black gas that blinds villains; these "blackout bombs" have had improvements made to them and are similar to those used by his predecessors.
- Although Norwegian by birth, Pieter Cross is a naturalized American citizen.
- Pieter Cross was born April 5, 1962.
- Pieter graduated from Harvard Medical School at the age of 19.
- Doctor Mid-Nite has his own web-site where he provides free medical advice to registered users. 
- The original concept sketches for Doctor Mid-Nite showed him wearing a full mask that covered his head entirely. However, he has never actually used this mask, and has only worn the half-mask that he is traditionally known to wear.
- Doctor Mid-Nite had been a vegetarian for a decade prior to dating Black Canary and practices yoga.
- Tim Drake is often mocked because his new "Red Robin" persona looks a lot like Dr. Mid-Nite's costume. 
- Doctor Mid-Nite (Volume 1)
- JSA #7–9
- JSA Secret Files and Origins #2
- JSA Classified #19–20
- JSA Classified #23–24
- 293 Appearances of Pieter Cross (New Earth)
- 101 Images featuring Pieter Cross (New Earth)
- 8 Quotations by or about Pieter Cross (New Earth)
- Character Gallery: Pieter Cross (New Earth)
Justice Society of America member