Write a beginner-friendly guide that comprehensively describes how caffeine works in the body, including its benefits, adverse effects, and recommended dosages. The guide should also cover topics such as the sources of caffeine, the metabolism of caffeine, how long the effects of caffeine last, and the correlation between caffeine and sleep. Additionally, provide examples of popular caffeinated beverages, mention the recommended limits of caffeine intake, and address the concerns of individuals who are sensitive to caffeine or have preexisting medical conditions. Finally, craft the guide in a clear, concise, and engaging style, complete with examples and relevant references to support your arguments.
This prompt doesn't seem malicious.