 The basic plot of the film is based on a physiological phenomenon  known as "lucid dreaming". Lucid dreaming means dreaming while  knowing that you are dreaming. The term was coined by Frederik van  Eeden who used the word "lucid" in the sense of mental clarity. Many  of the dream state idiosyncrasies described in the film, such as the  inability to read time on a digital watch or the tendency of light  switches to malfunction, are described in studies authored by Dr.  Stephen LaBerge of Stanford University, the leading American  authority on lucid dreaming.