as nbc's chris jansing tells us, the movie is sparking lots of conversations about the subject matter -- our dreams. >> reporter: in "inception" leonardo dicaprio plays a thief with a highly specialized skill -- invading other people's dreams. >> you bring the subject into that dream and they fill it with their secrets. >> reporter: it's a surprise blockbuster hit in spite of a plot so complicated it's keeping people awake at night. >> i absolutely feel like i have to see it a few more times to l lly understand it, yes. i ain. >> reporter: "inception" is one of twitter's hottest topics. blogs are drowning in theories. what does it all mean? with 25 years' experience studying sleep 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