Pym particles

Pym particles are a fictional chemical compound featured in comic books published by Marvel Comics. They first appeared as part of an unnamed experimental serum in "The Man in the Ant-Hill!" story from Tales to Astonish, Volume 1 #27 in January, 1962, which is also the same issue that introduced future costumed superhero, Hank Pym.

Scientist Hank Pym developed a serum that could reduce the size of any volume of matter to the relative size of an ant. In contrast, he also created a formula that could return said matter to it's original size. The chemical compound used in the creation of both formulas later came to be known as Pym particles. Pym particles can affect the size of a volume of matter (living or inorganic) by extracting and eschewing mass from an alternate dimension. The first time Hank Pym experimented with Pym particles, he used himself as a test subject. After reducing himself to but a fraction of his normal size, Pym fell down an ant-hill where he was assaulted by a colony of ants. Fortunately for him, one ant befriended him and helped to carry him back towards his lab where he crawled into a test tube containing the restorative formula to revert him back to normal. Fearing that the chemical mixture was too dangerous, he dispose of it immediately.

Weeks later however, Pym felt that such a tremendous discovery could not disappear forever, so he reinvented the formula as well as a special cybernetic helmet that allowed him to communicate with ants. Donning a red and black costume, he became the superhero Ant-Man for the first time.