Ant-Man and the Wasp was born when director Peyton Reed first saw an early version of Captain America: Civil War. In that film, Scott Lang (Paul Rudd) is recruited to help Captain America fight Iron Man, and ends up revealing in addition to shrinking, he can also grow very big. As audience members, we can see that…
Source: Gizmodo – How Both Captain America: Civil War and Infinity War Impact Ant-Man and the Wasp