An astrophysicist recounts how her team of researchers surfed the cosmos to map our local universe—and discovered the Laniakea supercluster, home of the Milky Way. You are here: on Earth, which is part of the solar system, which is in the Milky Way galaxy, which itself is within the extragalactic supercluster Laniakea. And how can we pinpoint our location so precisely? For 20 years, astrophysicist Hélène Courtois surfed the cosmos with international teams of researchers, working to map our local universe. In this book, Courtois describes this quest and the discovery of our home supercluster. Courtois explains that Laniakea (which means “immense heaven” in Hawaiian) is the largest galaxy structure known to which we belong; it is huge, almost too large to comprehend—about 500 million light-years in diameter. It contains about 100,000 large galaxies like our own, and a million smaller ones. Writing accessibly for nonspecialists, Courtois describes the visualization and analysis that allowed her team to map such large structures of the universe. She highlights the work of individual researchers, including portraits of several exceptional women astrophysicists—presenting another side of astronomy. Key ideas are highlighted in text insets; illustrations accompany the main text. The French edition of this book was named the Best Astronomy Book of 2017 by the astronomy magazine Ciel et espace. For this MIT Press English-language edition, Courtois has added descriptions of discoveries made after Laniakea: the cosmic velocity web and the Dipole and Cold Spot repellers. An engaging account of one of the most important discoveries in astrophysics in recent years, her story is a tribute to teamwork and international collaboration.