What causes the blue screen of death?(iphone 4s)?

What causes the blue screen of death?(iphone 4s)?

Added (1). GUYS I'm ASKING WHAT CAUSES THIS, NOT HOW TO FIX IT

Added (2). Like my phone won't turn on no matter what i do

There's one more step to try: restore as a NEW device (not from a backup). If the problem is solved, that means your backup has some sort of corruption in it.