Dr Owen Jeffries is an utterly brilliant mechanical scientist working for the Cavendish Laboratory attached to the University of Cambridge. He is a tenured Research Fellow with few teaching duties although he does have several graduate students reporting to him
Five years ago he joined a team of scientists investigating Dark Matter. The lead physicist, Dr Hawking, theorized that he could use an artifical black hole to generate sufficient gravity to cause dark matter to form a hybrid with regular matter in a bottle beyond the event horizon of the hole. Once it was formed, turning off the black hole should, in theory, allow the hybrid dark matter to be accessed.
What could possibly go wrong, you ask?
Dr Jeffries part of the project was to build the apparatus to Hawkings specifications. Which took all of Jeffries very considerable genius and talents.
On the day of the experiment, the entire team was present, safely behind an armored wall. The creation of the artificial black hole went well at first but then things started to go badly and the machine headed for an overload that would lead to an explosion of unknown power. Attempts to shut the experiment off at the control panel failed, somehow the reaction was feeding on itself.
There was only one chance to avoid the explosion and Dr Jeffries took it. He rushed into the room and started to manually control things with some safeguard fail safes that he had had the foresight to install.
He was partially successful. He was unable to stop the device exploding but he was able to considerably dampen the force of the blast. Instead of destroying the lab (or perhaps Cambridge or even the entire South of England) all that it did was to seriously injure Owen, causing the loss of his right arm and multiple other injuries.
The experiment itself had been partially successful and a small amount of dark matter had been created with just the tiniest amount of normal properties. Only perhaps 100 grams or so. Most of this was in a single chunk but tiny particles were embedded into Owen by the force of the explosion where they entered his blood stream and were carried to the brain.
The dark matter chunk and the particles are totally undetectable by conventional scientific instruments or senses. As far as the world is concerned, they just don't exist.
But somehow or other the particles embedded in Owens blood allowed him to perceive and operate on the dark matter. Or so Owen realized some weeks later after he got out of hospital.
In gratitude for his heroism, the college funded Owen's creation of a state of the art Bionic Arm to replace his lost one (and got the rights to the technology :-)). In total, it cost something on the order of 6 million pounds to build the arm.
Owen took the Dark Matter chunk that only he could interact with and studied it and came to an understanding of how it works. It took over a year but eventually he managed to construct a light weight suit interlaced with the Dark Matter.
The suit responds to his mental commands. He can use it to fly (albeit a little slowly), move quickly, and most importantly partly phase in and out of existence (he is still quite visible but is insubstantial)
The suit is extremely light and he usually just carries it in his pocket. It is the work of only a few seconds to take out the suit and put it on over his normal clothing (he just steps into it and pulls it up).
He realized that it was time to live up to the legacy of his (fictional) hero Spiderman. "With Great Power comes Great Responsibility". He was determined to become a Superhero.
He went on a year long exercise program both to fully mend after his injuries but also to prepare him for his coming adventures. During this program he learned to use the Dark matter to slightly hide his appearance, becoming world class in his stealth abilities.