Researchers have learned that they can train volunteers to meet aliens in their dreams by focussing on a half-dream state, ie. lucid dreaming, and seeking out ETs with their minds.
In this recent post I offered this idea: "The potential of the mind is immense. What if...the universe is all mind? What if the world you see when your brain interprets light beams caught on your retinas is really a creation of your mind? What if the whole of Planet Earth is, in effect, a giant holograph kept in place by mutual unconscious agreement? What if other collectives of mutual conscious agreement could create for themselves another kind of holograph - a parallel dimension, in other words?"
Is it really so difficult to accept that if a person determinedly sets out to visit other dimensions via their own will power - which, like most abilities, can be improved upon with practice and persistence, that it is possible to slip from one dimension to another? Contemporary terms like "alien" and "little grey men" can easily be replaced with older words such as "elf" or "god" or "mighty spirit". People have been travelling between dimensions for millennia - just ask a suitably skilled shamen, druid, witch or ritual magician.
To dismiss the experience by saying, "Oh, it's just a dream; it's all in your mind" is incredibly short-sighted when everything is all in your mind.