State the problem you tackle. What's the key research question? Again, in one sentence. (Note: For a more general essay, I'd adjust this slightly to state the central question that you want to address) Remember, your first sentence introduced the overall topic, so now you can build on that, and focus on one key question. within that topic. If you can not summarize your thesis / paper / essay in one key question, then you do not yet understand what you're trying to write about. Keep working at this step until you have a single, concise (and understandable question.