The sensation of falling when you sleep produces the "Hallucination hipnogógica".

It occurs when a person is about to fall asleep, this hallucination often paralyze the body and leaving only functioning eye muscles, heart, brain and breathing.

In this curious state one is believed to be awake, but the body feels asleep and awake head, so people usually suffer scare this curious feeling. There are times when the person sleeping in that state are awake, and immobility remains.

The most common feeling that people experience is the sensation of falling.