Many of us have encountered a version of what Zachary Horton calls the “cosmic zoom”—a visual journey through the many scales of the universe, from the microscopic to the cosmic. Most of our daily perception operates at a level of scale somewhere between that of quarks and galaxies, and it is this comfort with the immediately visible everyday world that the cosmic zoom unsettles. Horton uses the history of the cosmic zoom to explore how that scale itself has been constructed over the past seventy years. How has cosmic zoom media influenced scientific and popular understanding of the unseen world and how it may be known, accessed, and exploited? Horton insists that scale is the key to understanding and addressing major contemporary issues including climate change and big data, but people working on issues of scale in various disciplines often talk past each other. Horton starts by sketching four common ways of thinking about scale derived from cartography, physics, engineering/biology, and mathematics. He then shows how these concepts operate in various disciplines, explains why they don’t fit together, and puts forth a new, transdisciplinary theory and vocabulary of scale, one that links the natural sciences, humanities, and social sciences. In this ambitious work, scale becomes a foundation for rethinking the relationships between knowledge, mediation, and environment.