[History of blood platelets: from "molecules" to "cell"].

Historical annotations attached to the discovery of platelets as blood cells throughout the 19th century are reported. The so-called "minute molecules" were first connected with the formation of red and white blood cells, or of fibrin as well. The active role of platelets in coagulation was recognized only 30 years later. During that time, it became clear that these "molecules" were "cells", anatomical and physiological entities.