The body of a research paper is the section that supports the thesis and makes up the bulk of the paper. It is bookended at the front by the introductory materials and the thesis statement and at the back by the conclusion. The length of the body is proportional to the length of the paper as a whole. A five-page research paper, for example, would probably have a body that was between three-and-a-half and four pages long. A 60-page research paper on the other hand would probably have a body between 50 and 55 pages long.
In addition to text, the body of a research paper might include images, graphs, maps, and tables. Even if dozens of graphs or images informed the thesis, it is important to only include select items so that the paper does not become riddled with interruptions in the text. These items should be included and cited as per the rules set forth in the style guide that is being used. The same is true for all of the sources that are cited within the text of a research paper.
The main part of the text can be seen as having two purposes. The first is to support claims and assertions made in the thesis statement at the beginning of the paper. The second is to show the research that the writer completed in order to back up her thesis. Despite the fact that the thesis statement is at the beginning of the research paper, it is meant to be the culmination of all of the research that was completed and analyzed as part of the research project. All of this research and its various resulting conclusions that inform the thesis are detailed within the body.
One of the most important things to do when writing the body of a research paper is to organize the information. Don't worry about the writing being perfect and polished in the first stages of writing. Instead, focus on how the information will be presented within the paper. There are a number of ways to organize the body, but the most important thing to focus on is finding a way to present the information in a way that is clear and logical so that the reader will understand the purpose of the research as well as how it supports the claims made in the thesis statement.