Essential Ant Man, Vol.‎ 1 (Marvel Essentials)

Before he became one of the Avengers, Dr. Henry Pym was a man with big ideas. His contemporaries in the field of chemistry laughed when he first suggested his theories of spatial relations. They jeered at his beliefs that objects could be shrunk and later enlarged to their original size. They made Dr. Henry Pym feel very small indeed. And so, without their support and the proper funding, Henry created a serum based on his theories and then proceeded to experiment with it upon himself. And he shrunk to the size of an ant. That's where the nightmare began, as well as the beginnings of a hero.