Called “the Devil’s Dye” by Europeans, indigo dye paste has a long and turbulent history. For centuries it was produced on a small scale, and valued as the world’s finest source of blue. Traded as a hardened paste from India to Europe since before the Roman era, indigo was thought to be a mysterious rock capable of causing alchemical transformations. As trade expanded in the Early Modern Era, indigo made fortunes, enslaved masses, and fed revolutions. In the twentieth century synthetic indigo dyes caused a decline in natural indigo trade, but led to the development of modern organic chemistry. In the tropics, small-scale indigenous use of natural indigo persists today among artisans. In temperate climates, the word “indigo” is associated with jeans and jazz.