In the episode The Ricks Must Be Crazy from the TV series Rick and Morty, Rick and Morty got shrunken down when they entered the microverse that Rick created. There, the 2 of them, along with Zeep who created his miniverse, got shrunken into that.
I'm assuming that if Zeep could've transported himself to fight Rick in Rick's own universe, he would've done so. However, there must've be some scientific reason preventing him from doing so. Can someone elaborate on why this is? You can shrink down atoms, but making them larger just simply doesn't work that way?