Scientists at Sweden's Karolinska Institutet have been messing with people's heads, convincing them that they're just a foot tall.
The team wanted to investigate the theory that our bodies influence our perception of the world, so that the taller you are, the shorter distances appear to be.
Henrik Ehrsson and his colleagues had already been able to give people the sensation that they had three arms or had swapped bodies with another person, by synchronizing touches to the genuine and 'fake' bodies.
In these latest experiments, they managed to create the illusion of having either a doll-sized body or a 13-foot-tall one - showing for the first time, they say, that the size of our bodies influences the way we perceive the space around us.
"Tiny bodies perceive the world as huge, and vice versa," says Ehrsson.
The team assessed the subjects' perception of space by having them estimate the size of different blocks and then walk over to the blocks with their eyes shut. They found that the illusion of having a small body caused people to overestimate size and distance, with the opposite happening for large bodies.
"Even though we know just how large people are, the illusion makes us perceive other people as giants; it's a very weird experience," says Ehrsson, who also tried the experiment on himself.
He believes the illusion could have practical applications.
"It's possible, in theory, to produce an illusion of being a microscopic robot that can carry out operations in the human body, or a giant robot repairing a nuclear power plant after an accident," he says.