**Notes** > **Science** > **Psychology**    # General Notes - hypnagogic (or hypnagogic) hallucinations occur when falling asleep. - hypnopompic hallucinations occur when waking up. - hypnagogia refers to the two together. # External Reference Links - https://en.wikipedia.org/wiki/Hypnagogia (the transitional state from wakefulness to sleep). - https://en.wikipedia.org/wiki/Hypnopompia (the transitional state from sleep to wakefulness). - https://en.wikipedia.org/wiki/Oneirology (Sub-field of Psychology. The scientific study of dreams). - https://en.wikipedia.org/wiki/Neuroscience_of_sleep (Neuroscience of Sleep).