One moment you're sound asleep. The next moment you're wide awake. You try to move but you can't. You're aware of pressure on your body, as if someone is sitting on your chest. You try to open your mouth and scream, but you are paralyzed. You feel and hear something breathing in your ear, and you're convinced this is not a hallucination.
Welcome to the mysterious phenomenon known as Sleep Paralysis: an overlap between our REM and waking stages of sleep. In this fascinating video from TED-ed, Ami Angelowicz describes the science behind this terrifying anomalous state of consciousness.