The Tree Map is used for Classifying and/or Identifying Main Idea and Supporting Details. This type of map is probably visually familiar to most people. Looking much like a "family geneology tree", the top line of a tree map is where you write the category or the main idea of the topic. A connecting line comes down from the category and connects to individual sub-categories of supporting ideas. Below each sub-category add lines for the member of the category of specific ideas for the supporting ideas.