Once the first sentence has introduced the broad field, the next sentence can point to the specific area within that broad field.
As you may have noticed, the papers in the examples mentioned above introduced the subfield by mentioning 1) remission of some types cancer following accidental infection by Streptococcus pyogenes, 2) organic matter in soil as a source of nutrients for plants and of energy for microorganisms, and 3) imaging techniques to visualize the 3-dimensional structure of the materials and components of batteries on nanoscale.
You can do this by describing the research problem you considered or the research question you asked (in the main body of the paper, you will offer the solution to the problem or the answer to the question) and by briefly reviewing any other solutions or approaches that have been tried in the past.
Now that you have given the background and set the context, the last part of the Introduction should specify the objectives of the experiment or analysis of the study described in the paper.
In the introduction, you are attempting to inform the reader about the rationale behind the work, and to justify why your work is essential in the field.
The introduction does not have a strict word limit, unlike the abstract, but it should be as concise as possible.The introduction is the place to highlight any weaknesses in the experiment from the start.For example, an ideal experiment should have perfectly randomized samples, but there are many good reasons why this is not always possible.You should assume that your paper is aimed at someone with a good working knowledge of your particular field.For example, a paper about evolutionary adaptations need not go into too much detail about Darwin – it’s assumed your reader already has this knowledge..It can be a tricky part of the paper to write, so many scientists and researchers prefer to write it last, to make sure they haven’t missed anything important.For a longer research paper, where you use an outline, it can be useful to structure your introduction around the outline. The introduction gives an overall review of the paper, but does address a few slightly different issues from the abstract.A behavioral science paper only needs to mention Pavlov and Skinner in passing, as their theories are standard for any first year undergraduate.Like in any good Hollywood movie, the first task of the introduction is to set the scene.As long as you warn the reader about this, so that they are aware of the shortcomings, then they can easily judge the validity of the research for themselves.This is much better than making them wait until you point the weaknesses out in the discussion.