The term hypnagogic is often used to refer both to the experiences we have in the transitional state from waking to sleeping as well as to the experiences that occur as we pass from sleeping to wakefulness. One can distinguish between these two experiences, however, and restrict hypnagogic to the transition from wakefulness to sleep. The complementary term to hypnagogic is hypnopompic, which refers to the semiconscious state we experience preceding waking.
Like the hypnagogic transition, the hypnopompic state is peculiarly susceptible to certain kinds of vivid hallucinations, usually visual or auditory (sometimes more acutely sensory) in nature. Dreamers report to have heard snatches of conversations, glimpsed visitors passing by the bed, or even smelled perfume or oranges. The experience is so real, that when fully awake, it is hard to believe that it was only a dream state.