If our planet is not unique, then the probability of the widespread existence of intelligent life is enormous. Moreover, throughout the history of mankind, aliens have had enough time to make themselves known. So where are they? What are they? And if we find them, what will it turn out to be? Scientists of various professions - astronomers, physicists, cosmologists, biologists, anthropologists - are looking for answers to these questions, exploring all aspects of the problem. This includes the search for planets and satellites on which life is likely, and the possible structure of alien consciousness, and stories of alien abductions, and the depiction of “alien” in science fiction and cinema. To write the book, Professor Jim Al-Khalili assembled a team of scientists and thinkers, world leaders in their fields, including such stars as Martin Rees, Ian Stewart, Seth Shostak, Nick Lane and Adam Rutherford. Together they represent the whole range of issues and achievements of modern science in this search, and each of them makes its own unique contribution.