An ingenious discovery . . . dismissed as a dangerous lie.

In 1628, anatomist and physician William Harvey made a controversial claim: that blood circulated continuously through the body, pumping from the heart through the blood vessels into the tissues and then returning to the heart. His research contradicted many anatomy "experts" of the time. In the seventeenth century, European physicians did not go against the ancient Greek and Roman thinkers who'd created the foundations of Western medicine. But what if those foundations were wrong?

This is the story of how humans came to understand the circulatory system. And Harvey's work is only one part of that story. Discover the breakthroughs of scientists and scholars who dared to think outside the box, from Ibn al-Nafis, an Arab Muslim scholar who discovered pulmonary circulation; to Marcello Malpighi, who studied capillaries; to Joseph Priestley and Antoine Lavoisier, who figured out oxygen's role; and beyond!