The Pym Particles are special particles discovered by Dr. Henry Pym that can shrink or expand almost anything.
Pym Particles were first discovered by Dr. Henry Pym in his research work. He then built a device that contain the special particles to grow like a giant or shrink like an ant naming himself Ant/Giant Man while he injected Janet Van Dyne with the particles that shrunk her to the size of a wasp and gave her stingers naming herself The Wasp.
The Big House, Ultron guards, and the supervillain prisoners are the examples of the effects of Pym Particles which they were shrunk into a size of an ant while the building is shrunk into a size of a doll house.
However, due to long exposure and use of the Pym Particles cause Janet and Hank to evolve far beyond human capacity. For example like Wasp can grow big and Hank can both grow and shrink in size.
When Ant Man's suit was stolen by Scott Lang he used Pym Particles to steal money with Pym Discs but they were unsuccessful. After settling the issue and getting his daughter back Hank allowed him to continue being Ant-Man.