Have you ever seen something in front of you, and minutes later it was no longer there? Have you heard someone calling your name in an empty house? Have you ever felt someone walk behind you and then turned around to find that no one was there? These are different types of hallucinations. When we hear the word hallucinations, we always think of psychiatric institutions, schizophrenic patients, and madmen. But this is wrong information, as hallucinations may occur to any normal person if they are exposed to poisoning, illness, or injury in an accident, and they may occur to some of them even just by waking up suddenly.