The document outlines the investigation stage of a design cycle which consists of: introducing the unit, researching the problem, creating a design brief and specification, a test plan, and evaluating performance. It then provides more details on writing an introduction, including clearly stating the problem, considering what needs to be achieved like educating an audience and promoting a technology, and reflecting on how those things can be achieved. The introduction should also relate the problem personally and to society, and link it to the area of interaction being studied.