In the summer of 1674, in the city of Delft, Antoni van Leeuwenhoek discovered, looking through a tiny lens, the microscopic world. At the same time, in the attic of a nearby house, Johannes Vermeer used another optical instrument-a camera obscura-to experiment with light and thus create the brightest paintings that the world has ever contemplated. From then on, advances in physics, astronomy, chemistry and anatomy made way for modern science, transforming our view of the world and how to reflect it. An extraordinary revolution that Laura J. Snyder narrates in The Eye of the Observer with exquisite sensitivity: the search for knowledge through the look and life of two men who probably never got to know each other.