To be effective, scientific and technical documents have to limit their scope, the depth and breadth of their investigations. A scientific or technical report limits the scope of its discussions in response both to the boundaries of the inquiry itself and to the purpose and expertise of its audience. See Document Density.
A short statement of the scope of a document, describing what will be discussed, and what will not be discussed is often included as part of the introduction. In the following example, the author narrows the scope of the discussion of neural systems that control locomotion from humans or animals in general to one specific vertebrate, the lamprey.
Since the late 1960s, my colleagues and I have been attempting to unravel the design of the neural systems that coordinate locomotion in various experimental animals in hopes that this research will help scientists understand some of the intricacies of the human nervous system. Much is yet to be learned, but we have finally produced a blueprint for the neural networks responsible for movement in a simple vertebrate, a type of jawless fish known as a lamprey.
--Sten Grillner, "Neural Networks for Vertebrate Locomotion," Scientific American