All living things are either Eukarya, Bacteria or Archaea. These three broadest categories in the classification of life are called domains. Classifying organisms is nothing new for people as people have been concerned about classifying organisms for thousands of years. Aristotle the Greek philosopher was the first person to have classified organisms about 2000 years ago. Aristotle’s classification is still used today for classifying any new organisms that are discovered. Later on Carl Linnaeus worked on the already discovered model of Aristotle to create a different kind of classification system.