ALIENS could be among us - but we just cannot recognize them, Britain's top astronomer has said.
The Sun reported that Lord Martin Rees said the visitors might be in a form beyond human understanding.
Lord Rees, president of the Royal Society academy of science and also astronomer to the Queen, said: "They could be staring us in the face and we just don't recognize them."
The respected professor went on: "The problem is that we're looking for something very much like us, assuming that they at least have something like the same mathematics and technology.
"I suspect there could be life and intelligence out there in forms that we can't conceive.
"Just as a chimpanzee can't understand quantum theory, it could be there are aspects of reality which are beyond the capacity of our brains."
Lord Rees' comments raise the possibility of aliens being here - in the shape of anyone or anything.
He spoke out shortly after hosting the first conference on the possibility of alien life in the Royal Society's 350-year-history.
He also told highbrow Prospect magazine better telescopes meant the chance of finding life on other planets was "greater than ever."