From the distant past to the present, with fingers and felt-tipped pens, metallic powders and gel pots, humans have been drawn to lining their eyes. The aesthetic trademark of figures ranging from Nefertiti to Amy Winehouse, eyeliner is one of our most enduring cosmetic tools; ancient royals and Gen Z beauty influences alike would attest to its uniquely transformative power. It is undeniably fun-yet it is also far from frivolous. Seen through Zahra Hankir's (kohl-lined) eyes, this ubiquitous but seldom-examined product becomes a portal to history, proof both of the stunning variety among cultures across time and space and of our shared humanity. Through intimate reporting and conversations-with nomads in Chad, geishas in Japan, dancers in India, drag queens in New York, and mare-Eyeliner embraces the rich history and significance of its namesake, especially among communities of color. What emerges is an unexpectedly moving portrait of a tool that, in various corners of the globe, can signal religious devotion, attract potential partners, ward off evil forces, shield eyes from the sun, transform faces into fantasies, and communicate volumes without saying a word. Delightful, surprising, and utterly absorbing, Eyeliner is a fascinating tour through streets, stages, and bedrooms around the world, and a thought-provoking reclamation of a key piece of our collective history.