This book explores the impact of medical discourse and diagnostic technologies on the formation, representation, and reception of modern architecture. It challenges the normal understanding of modern architecture by proposing that the architecture of the early twentieth century was shaped by the dominant medical obsession of its time: tuberculosis and its primary diagnostic tool, the X-ray. If architectural discourse has from its beginning associated building and body, the body that it describes is the medical body, reconstructed by each new theory of health. Modern architects presented their architecture as a kind of medical instrument for protecting and enhancing the body. X-ray technology and modern architecture were born around the same time and evolved in parallel. While the X-ray exposed the inside of the body to the public eye, the modern building unveiled its interior, inverting the relationship between private and public. Colomina suggests that if we want to talk about the state of the art in buildings, we should look to the dominant obsessions about illness and the latest techniques of imaging the body—and ask what effects they may have on the way we conceive architecture.