On their very cool website, Marvel shows various things about the Ant-Man like his size ratio compared to other things both at full height and shrunk down. They also go into details about his telepathic helmet he uses to control ants and most importantly as shown by the graphic below… the shrinking is made possible by Pym Particles, which reduces the distance between atoms. Now I'm not Neil Degrasse Tyson, but at least that sounds scientific.
Also, the new TV trailer below shows us new footage form the film including Scott Lang showing off what he can do to his crew.
Ant-Man opens July 17th.