https://motherboard.vice.com/en_us/article/ywxjvg/steel-ball-control-dreams-dormio-mit-hypnagogia

When is a sleeper actually asleep?
There is a borderland between waking life and the uncharted wilderness of sleep that we all traverse each night, but we rarely stop to marvel at the strangeness of this liminal world. If we do, we find that it is full of hallucinations both wonderful and terrifying, a mental goulash of reality and fantasy.

Usually we pass through this state of half-wakefulness on our way to deep sleep within minutes. We may experience microdreams during the transition, but the content of these microdreams appear to be random and we usually don’t have any memory of them when we wake. A team of researchers led by MIT master's student Adam Horowitz wants to change that.