Summary : What is a UFO? Alien ships with mysterious aliens? Or maybe, This is a different form of life. CM existing on Earth in a dimension invisible to us? Are these mysterious phenomena mentioned by the Bible and other ancient sources? The book examines the history of mankind's contacts with unidentified flying objects throughout the millennial history of civilizations - from ancient times to the present day. There is evidence of recent meetings of people with the messengers of the “invisible world”, the opinions of scientists and researchers of the unknown. The picture is supplemented by declassified information from the archives of military departments of a number of countries. The publication is provided with personal and subject indexes, as well as drawings of witnesses of the landing of aliens .