Since olden times, many people have claimed to witness extraterrestrial beings or aliens. These life forms are called extraterrestrial because they are believed to originate from other worlds. While many people refuse to accept the idea of their existence, many scientists consider extraterrestrial life to be plausible, especially considering their supposed history within human life. These scientists maintain that billions of years ago, it was the genetic complexity of organisms that brought humans into being, and this same genetic complexity could have also brought aliens to life. Some say that these creatures resemble the form of humans but they generally look spine-chilling. Though there is still no direct evidence of their existence, several photographs have been released by eyewitnesses to prove that they actually exist. Here are 25 controversial UFO photographs ever released. via YouTube.