If the essay title is in the form of a question, then the introduction will need to outline your answer to the question. These approaches may not work in all introductions, for example ...

At the beginning of the Introduction ... The three examples below are suitable objects of the document for the three tasks shown above, respectively. This paper clarifies the role of CxHc on ...

An introduction should teach readers enough about the subject to read the paper, and should lead them through the topics to the experiment. Hand out an excerpted introduction of a scientific paper, ...