Gone are the days of little green men.
An "extremely tiny super-intelligent entity" is the newly proposed idea of what aliens are.
A NASA scientist for the Intelligent Systems Division believes that the current idea of aliens is far too narrow.
Silvano P Colombano claims that aliens may have already visited Earth, and humanity just missed it.
"I simply want to point out the fact that the intelligence we might find and that might choose to find us - if it hasn't already - might not be at all be produced by carbon based organisms like us," he wrote.
He believes that it is not outside the realm of possibility that alien life has gone beyond human technology, and may have even mastered interstellar travel.
His thoughts are written in a paper initially presented at a Decoding Alien Intelligence' workshop in March.
He says that we need to "revisit even our most cherished assumptions".
"Our typical life-spans would no longer be a limitation... and the size of the 'explorer' might be that of an extremely tiny super-intelligent entity."
He's called for physicists to take part in "speculative physics". He's asking for theories to be grounded in reality, but "with some willingness to stretch possibilities as to the nature of space time and energy."