A study with echoes of the movie Inception has shown how people who control their dreams engage specific parts of the brain.
The research provides a window into the sleep state and could be a first step towards "reading" dreams, say scientists.
It involved scanning the brains of "lucid" dreamers - people who are aware they are dreaming and can control their actions in dreams.
The learned skill offers scientists an opportunity to investigate the brain activity involved in dreaming.
"Dreaming is not just looking at a dream movie," said researcher Dr Martin Dresler, of the Max Planck Institute of Psychiatry in Munich, Germany. "Brain regions representing specific body motions are activated."
The scientists told participants to make a series of left and right hand movements separated by a series of eye movements after entering a lucid dream state.
The findings, published in the journal Current Biology, showed for the first time that neural activity in the brain's sensorimotor cortex can be related to body actions in dreams.
Co-author Dr Michael Czisch, also from the Max Planck Institute, said dream research was normally difficult because spontaneous dream activity cannot be experimentally controlled.
Lucid dreaming in combination with neuroimaging and sleep monitoring may in future make it possible to predict dreamed content by analysing brain activity patterns, the researchers believe.
"The lucid dreamer gains insight into a very complex state: sleeping, dreaming, but being consciously aware of the dream state," said Dr Dresler. "This may inform us about concepts of consciousness."