Hi I'm Stephanie Gallagher for About.com. Today I'll show you some tips for writing an expository essay from our Homework Tips site.An expository essay is simply an essay that expresses an idea and backs it up with facts. It could be an essay that describes how to do something or one that analyzes events, ideas or objects.A lot of times, expository essays are written in response to a prompt asking, such as:An expository essay has the same basic structure as any essay. You will want to have an introductory paragraph, body paragraphs and a summary.The introductory paragraph should capture the reader's attention with the first sentence. This should be something unusual that makes the reader think or raises a question in his or her mind. Then write a sentence or two that builds on the opening sentence and prepares the reader for your thesis statement. In this example, we're answering the question of why someone would pay that much money for a school bus and introducing the topic of the essay, which is Rosa Parks.The thesis statement wraps up the introduction, and at the same time, it asserts the point of your essay and provides an angle or structure to your argument. In this example, we're talking about Rosa Parks' important role in the civil rights movement.The body paragraphs expand on the thesis statement.In the body, you will build on the ideas you introduced in the thesis statement with supporting evidence. That evidence is typically statistics or facts you've gleaned from books, journals or research.The body is also the place to flesh out your arguments and provide a context for your assertions. In this example, we talk about how courageous it was for Rosa Parks to take that stance, given the social and political climate of the country at the time.Finally, your conclusion summarizes your key points and reasserts the claim of your thesis. Thanks for watching. For more great tips just like these, join us on the web at Education.About.com.