[mailslot]

If you stay partially aware as you fall asleep, you’ll see a ton of geometric hallucinations. It’s just the way things work.

[sleepybrett]

The scientists in the article are trying to get to a 'why'.

[fallingfrog]

Happens to me more upon waking up. But it's a cool phenomenon either way, and to my mind it's an indication that tripping is a normal thing for the human brain to do sometimes, and probably not harmful.