Ever wonder why soap bubbles become invisible right before they pop? Or why lenses are so blue they look purple? How is it possible to image black holes at the heart of distant galaxies? The answer to all these questions is Interference. This book tells the story of the science of optical interferometry - mankind's most sensitive form of measurement - and of the scientists who tamed light to make outstanding discoveries, from lasers and holograms to astronomy and quantum physics. In the past several years, interferometry has been used to discover exoplanets orbiting distant stars, to take the first image of a black hole, to detect the first gravitational waves and to create the first programmable quantum computer. This list of achievements points to the fertile and active field of interferometry for which this book provides a convenient and up - to - date guide for a wide audience interested in the science of light.