Micrographia

Hooke began his observations with studies of non-living materials, such as woven cloth and frozen urine crystals, after which he proceeded to investigations of plant and animal life. He published the first studies of insect anatomy, giving a lucid account of the compound eye of the fly, and illustrating the microscopic details of such structures as apian wings, flies' legs and feet, and the sting of the bee. His famous and dramatic portraits of the flea and louse, a frightening eighteen inches long, are hardly less startling today than they must have been to Hooke's contemporaries. His botanical observations include the first description of the plant-like form of molds, and of the honeycomb-like structure of cork, which last he described as being composed of "cellulae"--Thereby coining the modern biological usage of the work "cell" to describe the basic microscopic units of tissue