dr. rosenberg isn't surprised. >> at every cocktail party or family gathering i get questioned about dreams. really being able to understand them is still not a perfect science. >> reporter: still, "inception" isn't all science fiction. >> well, the movie itself does demonstrate that people can have more control over their dreams. >> reporter: scientists call it lucid dreaming. it takes training and practice, but sleep experts can teach you to be aware in the middle of a dream that you are in a dream. training that includes looking for clues, things that nevehappr en never happen in real life, for example, telling you that however real things might look and feel in your dream, they're not. but that's as far as it goes. scientists don't foresee a o-like ability to invade our dreams. >> it's the great mystery. what is it? what happens when i close my eyes and go to sleep? >> it's only when we wake up that we realize something was actually strange. >> reporter: for now, the answer left in large part to movie makers' imaginations. in the meantime, thousands of people are taking matters into the