As of today, we are still sending messages to the stars: messages that, so far, have not been answered. For more than fifty years, we've been unsuccessfully searching for any evidence of intelligent extraterrestrial life. But the discovery of thousands of exoplanets has meant the hope of finding them is higher than ever. First contact with alien intelligence will become a reality in the future, so we must understand how to communicate. While SETI searches for extra-terrestrial life, METI are the body communicating with the stars in the hope of receiving an answer. But it's hard to imagine what form anybody listening in space will take and what their intelligence could be like, so it's difficult to compose a message. What kind of universal language could we use? What should the content of the message be? How could we introduce ourselves to an unknown civilization? Could it be risky to send messages into the unknown in case the recipients were hostile? Given the distance between stars, communication will be tricky if not almost impossible. But if a message could eventually be decoded and answered, it would radically transform our consciousness as species and our place in the universe. A message from the stars would change life on Earth forever.