My theory is that the universe was created by the death of a type of star out of sight from our current technology which means "Our Universe" goes as far as the edge of the hypernova blast radius. Beyond that is space which is populated by other what I call Gx or Genesis stars which in turn will create hypernova remnants within which other universes will be able to develop.
So I feel that we are a multiverse but not as such stringy more microbial on a different level.