In this article, Renee Clary and James Wandersee describe the beginnings of "Classification," which lies at the very heart of science and depends upon pattern recognition. Clary and Wandersee approach patterns by first telling the story of the "Linnaean classification system," introduced by Carl Linnacus (1707-1778), who is credited with devising the formal system for naming species. The "binomen," or "Latin name" system, identifies an organism with a genus name and, within the genus, a species name. Species, the most exclusive category of classification, are those organisms with similar morphologies that can interbreed and produce fertile offspring. Thus, observation, organization, and categorization were key to scientific botanical approach, and teaching students how to observe nature outdoors was central to Linnaeus's methods. This can be incorporated into the classroom as a teacher-led discussion or group research project. Clary and Wandersee next provide a classification activity that can be done to help students learn pattern recognition and classification development. They conclude that classification activities develop student observation and organization skills and foster a more scientific frame of mind. Teaching the history of classification helps students appreciate the human side of science and understand that science evolves with new information.